Reiner E

General

Full name : Reiner Elsa

First name : Elsa

Mail : Institute for Medical Research and Occupational Health\; Ksaverska cesta 2\; POB 291\; HR10001 Zagreb

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Country : Croatia

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Website : \/\/www.11che.ru\/ereiner.html

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References (69)

Title : Mechanism of stereoselective interaction between butyrylcholinesterase and ethopropazine enantiomers - Sinko_2011_Biochimie_93_1797
Author(s) : Sinko G , Kovarik Z , Reiner E , Simeon-Rudolf V , Stojan J
Ref : Biochimie , 93 :1797 , 2011
Abstract : Stereoselectivity of reversible inhibition of butyrylcholinesterase (BChE; EC 3.1.1.8) by optically pure ethopropazine [10-(2-diethylaminopropyl)phenothiazine hydrochloride] enantiomers and racemate was studied with acetylthiocholine (0.002-250 mM) as substrate. Molecular modelling resulted in the reaction between BChE and ethopropazine starting with the binding of ethopropazine to the enzyme peripheral anionic site. In the next step ethopropazine 'slides down' the enzyme gorge, resulting in interaction of the three rings of ethopropazine through pi-pi interactions with W82 in BChE. Inhibition mechanism was interpreted according to three kinetic models: A, B and C. The models differ in the type and number of enzyme-substrate, enzyme-inhibitor and enzyme-substrate-inhibitor complexes, i.e., presence of the Michaelis complex and/or acetylated BChE. Although, all three models reproduced well the BChE activity in absence of ethopropazine, model A was poor in describing inhibition with ethopropazine, while models B and C were better, especially for substrate concentrations above 0.2 mM. However model C was singled out because it approaches fulfilment of the one step-one event criteria, and confirms the inhibition mechanism derived from molecular modelling. Model C resulted in dissociation constants for the complex between BChE and ethopropazine: 61, 140 and 88 nM for R-enantiomer, S-enantiomer and racemate, respectively. The respective dissociation constants for the complexes between acetylated BChE and ethopropazine were 268, 730 and 365 nM. Butyrylcholinesterase had higher affinity for R-ethopropazine.
ESTHER : Sinko_2011_Biochimie_93_1797
PubMedSearch : Sinko_2011_Biochimie_93_1797
PubMedID: 21740955

Title : 10th International Meeting on Cholinesterases. Preface -
Author(s) : Reiner E
Ref : Chemico-Biological Interactions , 187 :1 , 2010
PubMedID: 20595049

Title : Differentiation of EDTA-sensitive from EDTA-insensitive human serum esterases hydrolysing phenylacetate - Bosak_2008_J.Enzyme.Inhib.Med.Chem_23_521
Author(s) : Bosak A , Barlovic-Tusek B , Reiner E
Ref : J Enzyme Inhib Med Chem , 23 :521 , 2008
Abstract : The aim of this study was to differentiate the EDTA-sensitive from the EDTA-insensitive human serum esterases by evaluating their catalytic constants, K(M) and V(m), for the hydrolysis of phenylacetate (PA). Measurements were done at 37 degrees C in 0.1 M Tris/HCl buffer pH 7.4 and 8.4. The K(M,sen) and K(M,ins) constants were significantly different, 0.97 and 2.7 mM respectively, confirming that two esterases hydrolyse PA. The pH of the medium had no effect on K(M) values, and also no effect on V(m,sen) while V(m,ins) was two fold higher at pH 8.4 than at 7.4 further confirming the existence of two different enzymes. The stability of the esterases in aqueous media was also studied. EDTA-sensitive activity in buffer without CaCl(2) was extremely unstable; the time-course of inactivation followed a two-phase reaction kinetics, indicating that two EDTA-sensitive esterases hydrolyse PA. The EDTA-insensitive activity remained constant in aqueous media under the same experimental conditions.
ESTHER : Bosak_2008_J.Enzyme.Inhib.Med.Chem_23_521
PubMedSearch : Bosak_2008_J.Enzyme.Inhib.Med.Chem_23_521
PubMedID: 18665999

Title : Mechanisms of organophosphate toxicity and detoxication with emphasis on studies in Croatia - Reiner_2007_Arh.Hig.Rada.Toksikol_58_329
Author(s) : Reiner E , Radic Z , Simeon-Rudolf V
Ref : Arh Hig Rada Toksikol , 58 :329 , 2007
Abstract : This review comprises studies on the mechanisms of toxicity and detoxication of organophosphorus (OP) compounds done in Croatia in different research areas. One area is the synthesis of antidotes against OP poisoning and their in vivo testing in experimental animals. In vitro studies included in this review focus on the mechanisms of reversible inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), protection of cholinesterases from inhibition by OPs, and reactivation of phosphylated cholinesterases. The third area comprises distribution profiles of BChE and paraoxonase (PON) phenotypes in selected population groups and the detection of OPs and metabolites in humans. Finally, methods are described for the detection of OP compounds in human blood and other media by means of cholinesterase inhibition.
ESTHER : Reiner_2007_Arh.Hig.Rada.Toksikol_58_329
PubMedSearch : Reiner_2007_Arh.Hig.Rada.Toksikol_58_329
PubMedID: 17913688

Title : Application of recombinant DNA methods for production of cholinesterases as organophosphate antidotes and detectors - Taylor_2007_Arh.Hig.Rada.Toksikol_58_339
Author(s) : Taylor P , Reiner E , Kovarik Z , Radic Z
Ref : Arh Hig Rada Toksikol , 58 :339 , 2007
Abstract : To develop new avenues for synthesizing novel antidotes for organophosphate poisoning and for detection of the organophosphates, we have turned to recombinant DNA methods to synthesize cholinesterases with unusual properties. For antidotal therapy we describe mutations of the native mouse and human enzymes that allow for enhanced rates of oxime reactivation. Such enzymes, when localized in the circulation, would enable the circulating cholinesterase to become a catalytic rather than simply a stoichiometric scavenger. Hence, "oxime-assisted catalysis" provides a means for scavenging the organophosphates in the circulation thereby minimizing their tissue penetration and toxicity. Accordingly, the oxime antidote or prophylactic agent has a dual action within the circulation and at the tissue level. Second, through a novel chemistry, termed freeze-frame, click chemistry, we have used organophosphate conjugates of acetylcholinesterase as templates for the synthesis of novel nucleophilic reactivating agents. Finally, acetylcholinesterase can be modified through cysteine substitution mutagenesis and attachment of fluorophores at the substitution positions. When linked at certain locations in the molecule, the attached fluorophore is sensitive to organophosphate conjugation with acetylcholinesterase, and thus the very target of insecticide or nerve agent action becomes a detection molecule for organophosphate exposure.
ESTHER : Taylor_2007_Arh.Hig.Rada.Toksikol_58_339
PubMedSearch : Taylor_2007_Arh.Hig.Rada.Toksikol_58_339
PubMedID: 17913689

Title : Acetylcholinesterase: converting a vulnerable target to a template for antidotes and detection of inhibitor exposure - Taylor_2007_Toxicology_233_70
Author(s) : Taylor P , Kovarik Z , Reiner E , Radic Z
Ref : Toxicology , 233 :70 , 2007
Abstract : Applications of recombinant DNA technology, chemical synthesis on biological templates and fluorescence detection of organophosphorylation provide unexplored avenues for development of antidotes and approaches for remote detection of organophosphate nerve agents and pesticides. We discuss here how acetylcholinesterase (AChE), through appropriate mutations, becomes more susceptible to oxime reactivation. Since the reaction between organophosphate and the mutated enzyme remains rapid, regeneration of active enzyme by oxime becomes the rate-limiting step in the process to complete a catalytic cycle for generation of active enzyme. Accordingly, "Oxime-assisted Catalysis" by AChE provides a potential means for catalyzing the hydrolysis of organophosphates in plasma prior to their reaching the cellular target site. In turn, AChE, when conjugated with organophosphate, is employed as a template for 'click-chemistry, freeze-frame' synthesis of new nucleophilic reactivating agents that could potentially prove useful in AChE reactivation at the target site as well as in catalytic scavenging of organophosphates in plasma. Finally, substituted AChE molecules can be conjugated to fluorophores giving rise to shifts in emission spectra for detection of dispersed organophosphates. Since external reagents do not have to be added to detect the fluorescence change, the modified enzyme would serve as a remote sensor.
ESTHER : Taylor_2007_Toxicology_233_70
PubMedSearch : Taylor_2007_Toxicology_233_70
PubMedID: 17196318

Title : Pyridinium, imidazolium and quinuclidinium compounds: toxicity and antidotal effects against the nerve agents Tabun and Soman - Reiner_2006_Arh.Hig.Rada.Toksikol_57_171
Author(s) : Reiner E , Simeon-Rudolf V
Ref : Arh Hig Rada Toksikol , 57 :171 , 2006
Abstract : This paper discusses the toxicity and antidotal effects of 32 compounds. Screening studies have shown that these compounds combined with atropine are effective antidotes against the organophosphate nerve agents Tabun and/or Soman, having a therapeutic factor equal or greater than 2.0 when tested in mice or rats. We analysed the results of these studies, and recommend that these compounds should be studied in more detail simultaneously with conventional antidotes (PAM-2, HI-6, Toxogonin, TMB-4(Trimedoxime)) in order to assess whether they could broaden the choice of compounds now available for the treatment of organophosphate poisoning.
ESTHER : Reiner_2006_Arh.Hig.Rada.Toksikol_57_171
PubMedSearch : Reiner_2006_Arh.Hig.Rada.Toksikol_57_171
PubMedID: 16832972

Title : Acetylcholinesterase mutants: oxime-assisted catalytic scavengers of organophosphonates -
Author(s) : Kovarik Z , Radic Z , Simeon-Rudolf V , Reiner E , Taylor P
Ref : Chemico-Biological Interactions , 157-158 :388 , 2005
PubMedID: 16429526

Title : Mutant cholinesterases possessing enhanced capacity for reactivation of their phosphonylated conjugates - Kovarik_2004_Biochemistry_43_3222
Author(s) : Kovarik Z , Radic Z , Berman HA , Simeon-Rudolf V , Reiner E , Taylor P
Ref : Biochemistry , 43 :3222 , 2004
Abstract : Selective mutants of mouse acetylcholinesterase (AChE; EC 3.1.1.7) phosphonylated with chiral S(P)- and R(P)-cycloheptyl, -3,3-dimethylbutyl, and -isopropyl methylphosphonyl thiocholines were subjected to reactivation by the oximes HI-6 and 2-PAM and their reactivation kinetics compared with wild-type AChE and butyrylcholinesterase (EC 3.1.1.8). Mutations in the choline binding site (Y337A, Y337A/F338A) or combined with acyl pocket mutations (F295L/Y337A, F297I/Y337A, F295L/F297I/Y337A) were employed to enlarge active center gorge dimensions. HI-6 was more efficient than 2-PAM (up to 29000 times) as a reactivator of S(P)-phosphonates (k(r) ranged from 50 to 13000 min(-1) M(-1)), while R(P) conjugates were reactivated by both oximes at similar, but far slower, rates (k(r) < 10 min(-1) M(-1)). The Y337A substitution accelerated all reactivation rates over the wild-type AChE and enabled reactivation even of R(P)-cycloheptyl and R(P)-3,3-dimethylbutyl conjugates that when formed in wild-type AChE are resistant to reactivation. When combined with the F295L or F297I mutations in the acyl pocket, the Y337A mutation showed substantial enhancements of reactivation rates of the S(P) conjugates. The greatest enhancement of 120-fold was achieved with HI-6 for the F295L/Y337A phosphonylated with the most bulky alkoxy moiety, S(P)-cycloheptyl methylphosphonate. This significant enhancement is likely a direct consequence of simultaneously increasing the dimensions of both the choline binding site and the acyl pocket. The increase in dimensions allows for optimizing the angle of oxime attack in the spatially impacted gorge as suggested from molecular modeling. Rates of reactivation reach values sufficient for consideration of mixtures of a mutant enzyme and an oxime as a scavenging strategy in protection and treatment of organophosphate exposure.
ESTHER : Kovarik_2004_Biochemistry_43_3222
PubMedSearch : Kovarik_2004_Biochemistry_43_3222
PubMedID: 15023072

Title : In memoriam: Miroslav Brzin (13 April 1923- 8 August 1999) - Reiner_2004_Cholinergic.Mechanisms.CRC.Press__289
Author(s) : Reiner E
Ref : Cholinergic Mechanisms, CRC Press :289 , 2004
Abstract : http:\/\/www.crcnetbase.com/doi/abs/10.3109/9780203493878-43
ESTHER : Reiner_2004_Cholinergic.Mechanisms.CRC.Press__289
PubMedSearch : Reiner_2004_Cholinergic.Mechanisms.CRC.Press__289
PubMedID:

Title : Peripheral binding of ethopropazine to horse serum butyrylcholinesterase. -
Author(s) : Reiner E , Sinko G , Stuglin A , Simeon-Rudolf V
Ref : Cholinergic Mechanisms, CRC Press :673 , 2004
PubMedID:

Title : Kinetics of interaction of ethopropazine enantiomers with butyrylcholinesterase and acetylcholinesterase. -
Author(s) : Reiner E , Sinko G , Radic Z , Taylor P , Simeon-Rudolf V
Ref : Cholinergic Mechanisms, CRC Press :705 , 2004
PubMedID:

Title : Kinetics of ethopropazine binding to butyrylcholinesterase in the absence and presence of acetylthiocholine -
Author(s) : Reiner E , Sinko G , Bosak A , Simeon-Rudolf V , Radic Z , Taylor P , Stojan J , Golicnik M
Ref : In: Cholinesterases in the Second Millennium: Biomolecular and Pathological Aspects , (Inestrosa NC, Campos EO) P. Universidad Catolica de Chile-FONDAP Biomedicina :187 , 2004
PubMedID:

Title : Poster (19) Kinetics of ethopropazine binding to butyrylcholinesterase in the absence and presence of acetylthiocholine. -
Author(s) : Reiner E , Sinko G , Stuglin A , Simeon-Rudolf V , Radic Z , Taylor P , Stojan J , Golicnik M
Ref : In: Cholinesterases in the Second Millennium: Biomolecular and Pathological Aspects , (Inestrosa NC, Campos EO) P. Universidad Catolica de Chile-FONDAP Biomedicina :330 , 2004
PubMedID:

Title : Activity of cholinesterases in human whole blood measured with acetylthiocholine as substrate and ethopropazine as selective inhibitor of plasma butyrylcholinesterase - Reiner_2004_Arh.Hig.Rada.Toksikol_55_1
Author(s) : Reiner E , Bosak A , Simeon-Rudolf V
Ref : Arh Hig Rada Toksikol , 55 :1 , 2004
Abstract : A procedure is suggested for measuring acetylcholinesterase and butyrylcholinesterase activities in human whole blood using acetylthiocholine as a substrate and ethopropazine as a selective inhibitor of butyrylcholinesterase. The procedure is suitable for screening cholinesterase activities in routine and/or field tests.
ESTHER : Reiner_2004_Arh.Hig.Rada.Toksikol_55_1
PubMedSearch : Reiner_2004_Arh.Hig.Rada.Toksikol_55_1
PubMedID: 15137175

Title : Molar absorption coefficients for the reduced Ellman reagent: reassessment - Eyer_2003_Anal.Biochem_312_224
Author(s) : Eyer P , Worek F , Kiderlen D , Sinko G , Stuglin A , Simeon-Rudolf V , Reiner E
Ref : Analytical Biochemistry , 312 :224 , 2003
Abstract : The Ellman method for assaying thiols is based on the reaction of thiols with the chromogenic DTNB (5,5'-dithiobis-2-nitrobenzoate) whereby formation of the yellow dianion of 5-thio-2-nitrobenzoic acid (TNB) is measured. The TNB molar absorption coefficient, 13.6 x 10(3)M(-1)cm(-1), as published by Ellman in 1959 has been almost universally used until now. Over the years, however, slightly different values have been published, and it has further been shown that TNB reveals thermochromic properties. This should be taken into account when the Ellman method is used for determination of enzyme activities, such as in cholinesterase assays. Our data show that the absorbance spectra of TNB are shifted to longer wavelengths when temperature increases, while absorbance maxima decrease. Our recommended molar absorption coefficients at 412 nm are 14.15 x 10(3)M(-1)cm(-1) at 25 degrees C and 13.8 x 10(3)M(-1)cm(-1) at 37 degrees C (0.1M phosphate buffer, pH 7.4). Molar absorption coefficients for other temperatures and wavelengths are included in the paper.
ESTHER : Eyer_2003_Anal.Biochem_312_224
PubMedSearch : Eyer_2003_Anal.Biochem_312_224
PubMedID: 12531209

Title : Acetylcholinesterase active centre and gorge conformations analyzed by combinatorial mutations and enantiomeric phosphonates - Kovarik_2003_Biochem.J_373_33
Author(s) : Kovarik Z , Radic Z , Berman HA , Simeon-Rudolf V , Reiner E , Taylor P
Ref : Biochemical Journal , 31 :33 , 2003
Abstract : A series of eight double and triple mutants of mouse acetylcholinesterase (AChE; EC 3.1.1.7), with substitutions corresponding to residues found largely within the butyrylcholinesterase (BChE; EC 3.1.1.8) active-centre gorge, was analysed to compare steady-state kinetic constants for substrate turnover and inhibition parameters for enantiomeric methylphosphonate esters. The mutations combined substitutions in the acyl pocket (Phe(295)-->Leu and Phe(297)-->Ile) with the choline-binding site (Tyr(337)-->Ala and Phe(338)-->Ala) and with a side chain (Glu(202)--> Gln) N-terminal to the active-site serine, Ser(203). The mutations affected catalysis by increasing K (m) and decreasing k (cat), but these constants were typically affected by an order of magnitude or less, a relatively small change compared with the catalytic potential of AChE. To analyse the constraints on stereoselective phosphonylation, the mutant enzymes were reacted with a congeneric series of S (P)- and R (P)-methylphosphonates of known absolute stereochemistry. Where possible, the overall reaction rates were deconstructed into the primary constants for formation of the reversible complex and intrinsic phosphonylation. The multiple mutations greatly reduced the reaction rates of the more reactive S (P)-methylphosphonates, whereas the rates of reaction with the R (P)-methylphosphonates were markedly enhanced. With the phosphonates of larger steric bulk, the enhancement of rates for the R (P) enantiomers, coupled with the reduction of the S (P) enantiomers, was sufficient to invert markedly the enantiomeric preference. The sequence of mutations to enlarge the size of the AChE active-centre gorge, resembling in part the more spacious gorge of BChE, did not show an ordered conversion into BChE reactivity as anticipated for a rigid template. Rather, the individual aromatic residues may mutually interact to confer a distinctive stereospecificity pattern towards organophosphates.
ESTHER : Kovarik_2003_Biochem.J_373_33
PubMedSearch : Kovarik_2003_Biochem.J_373_33
PubMedID: 12665427

Title : Organophosphorus compounds and esterases: current research topics concerning the toxicity of and protection against organophosphates - Reiner_2001_Arh.Hig.Rada.Toksikol_52_323
Author(s) : Reiner E
Ref : Arh Hig Rada Toksikol , 52 :323 , 2001
Abstract : This brief review describes the reactions of organophosphorus compounds with cholinesterases neuropathy target esterase and phosphoric triester hydrolases with respect to their toxicity It also describes antidotes protectors and decontaminating agents against organophosphates
ESTHER : Reiner_2001_Arh.Hig.Rada.Toksikol_52_323
PubMedSearch : Reiner_2001_Arh.Hig.Rada.Toksikol_52_323
PubMedID: 11770330

Title : Cholinesterase: substrate inhibition and substrate activation - Reiner_2000_Pflugers.Arch_440_R118
Author(s) : Reiner E , Simeon-Rudolf V
Ref : Pflugers Arch , 440 :R118 , 2000
Abstract : The relationship between activities and substrate concentrations (pS-curves) was analysed for reactions of acetylcholinesterase (EC 3.1.1.7) and butyrylcholinesterase (EC 3.1.1.8). Catalytic constants Km, Kss, Vm, n and b were calculated from the Michaelis, Haldane, Hill and Webb equations in order to assess whether a given substrate also acts as an inhibitor or activator. It is suggested that the term substrate inhibition should only be attributed to substrates revealing bell-shaped pS-curves, while the terms apparent substrate inhibition or apparent substrate activation should relate to calculated values of the catalytic constants.
ESTHER : Reiner_2000_Pflugers.Arch_440_R118
PubMedSearch : Reiner_2000_Pflugers.Arch_440_R118
PubMedID: 11005636

Title : Comparison of protocols for measuring activities of human blood cholinesterases by the Ellman method - Reiner_2000_Arh.Hig.Rada.Toksikol_51_13
Author(s) : Reiner E , Sinko G , Skrinjaric-Spoljar M , Simeon-Rudolf V
Ref : Arh Hig Rada Toksikol , 51 :13 , 2000
Abstract : This paper presents a protocol for routine assays of human blood cholinesterase activities which separates erythrocytes from plasma by centrifugation and measures acetylcholinesterase activity in unwashed erythrocytes and butyrylcholinesterase activity in the plasma. The recommended substrate for both enzymes is 1.0 mM acetylthiocholine. The protocol is compared with other two recommended protocols for the activity measurements of the two enzymes using the Ellman method. The paper discusses the advantages and disadvantages of each and concludes with a proposal for an international agreement between laboratories for the evaluation of a standardized protocol.
ESTHER : Reiner_2000_Arh.Hig.Rada.Toksikol_51_13
PubMedSearch : Reiner_2000_Arh.Hig.Rada.Toksikol_51_13
PubMedID: 11059068

Title : Recommended nomenclature system for the paraoxonases -
Author(s) : La Du BN , Furlong CE , Reiner E
Ref : Chemico-Biological Interactions , 119-120 :599 , 1999
PubMedID: 10421500

Title : Reversible inhibition of acetylcholinesterase and butyrylcholinesterase by 4,4'-bipyridine and by a coumarin derivative - Simeon-Rudolf_1999_Chem.Biol.Interact_119-120_119
Author(s) : Simeon-Rudolf V , Kovarik Z , Radic Z , Reiner E
Ref : Chemico-Biological Interactions , 119-120 :119 , 1999
Abstract : Inhibition of recombinant mouse wild type AChE (EC 3.1.1.7) and BChE (EC 3.1.1.8), and AChE peripheral site-directed mutants and human serum BChE variants by 4,4'-bipyridine (4,4'-BP) and the coumarin derivative 3-chloro-7-hydroxy-4-methylcoumarin (CHMC) was studied. The enzyme activity was measured with acetylthiocholine as substrate. Enzyme-inhibitor dissociation constants for the catalytic and peripheral sites were evaluated from the apparent dissociation constants as a function of the substrate concentration. Inhibition by 4,4'-BP of AChE, BChE and the AChE mutant Y72N/Y124Q/W286A, was consistent with inhibitor binding to both catalytic and peripheral sites. The dissociation constants for the peripheral site were about 3.5-times higher than for the catalytic site. The competition between CHMC and substrate displayed two binding sites on the AChE mutants Y72N, Y124Q, W286A and W286R, and on the atypical and fluoride-resistant BChE variants. The dissociation constants for the peripheral site were on average two-times higher than for the catalytic site. CHMC displayed binding only to the catalytic site of Y72N/Y124Q/W286A mutant and only to the peripheral site of w.t. AChE and the human usual BChE. Modelling of the 4,4'-BP and CHMC binding to wild type mouse AChE substantiated the difference between the inhibitors in their mode of binding which was revealed in the kinetic studies.
ESTHER : Simeon-Rudolf_1999_Chem.Biol.Interact_119-120_119
PubMedSearch : Simeon-Rudolf_1999_Chem.Biol.Interact_119-120_119
PubMedID: 10421445

Title : Amino acid residues involved in the interaction of acetylcholinesterase and butyrylcholinesterase with the carbamates Ro 02-0683 and bambuterol, and with terbutaline - Kovarik_1999_Biochim.Biophys.Acta_1433_261
Author(s) : Kovarik Z , Radic Z , Grgas B , Skrinjaric-Spoljar M , Reiner E , Simeon-Rudolf V
Ref : Biochimica & Biophysica Acta , 1433 :261 , 1999
Abstract : In order to identify amino acids involved in the interaction of acetylcholinesterase (AChE; EC 3.1.1.7) and butyrylcholinesterase (BChE; EC 3.1.1.8) with carbamates, the time course of inhibition of the recombinant mouse enzymes BChE wild-type (w.t.), AChE w.t. and of 11 site-directed AChE mutants by Ro 02-0683 and bambuterol was studied. In addition, the reversible inhibition of cholinesterases by terbutaline, the leaving group of bambuterol, was studied. The bimolecular rate constant of AChE w.t. inhibition was 6.8 times smaller by Ro 02-0683 and 16000 times smaller by bambuterol than that of BChE w.t. The two carbamates were equipotent BChE inhibitors. Replacement of tyrosine-337 in AChE with alanine (resembling the choline binding site of BChE) resulted in 630 times faster inhibition by bambuterol. The same replacement decreased the inhibition by Ro 02-0683 ten times. The difference in size of the choline binding site in the two w.t. enzymes appeared critical for the selectivity of bambuterol and terbutaline binding. Removal of the charge with the mutation D74N caused a reduction in the reaction rate constants for Ro 02-0683 and bambuterol. Substitution of tyrosine-124 with glutamine in the AChE peripheral site significantly increased the inhibition rate for both carbamates. Substitution of phenylalanine-297 with alanine in the AChE acyl pocket decreased the inhibition rate by Ro 02-0683. Computational docking of carbamates provided plausible orientations of the inhibitors inside the active site gorge of mouse AChE and human BChE, thus substantiating involvement of amino acid residues in the enzyme active sites critical for the carbamate binding as derived from kinetic studies.
ESTHER : Kovarik_1999_Biochim.Biophys.Acta_1433_261
PubMedSearch : Kovarik_1999_Biochim.Biophys.Acta_1433_261
PubMedID: 10446376

Title : 3-Hydroxyquinuclidinium derivatives: synthesis of compounds and inhibition of acetylcholinesterase - Reiner_1999_Chem.Biol.Interact_119-120_173
Author(s) : Reiner E , Skrinjaric-Spoljar M , Dunaj S , Simeon-Rudolf V , Primozic I , Tomic S
Ref : Chemico-Biological Interactions , 119-120 :173 , 1999
Abstract : Four compounds were prepared: 3-hydroxy-1-methylquinuclidinium iodide (I), 3-(N,N-dimethylcarbamoyloxy)-1-methylquinuclidinum iodide (II), and two conjugates of I and II with 2-hydroxyiminomethyl-3-methylimidazole in which two parts of the molecule were linked by -CH2-O-CH2- (III and IV). III and IV are new compounds and their synthesis and physical data were given. All compounds were tested as inhibitors of human erythrocyte acetylcholinesterase (EC 3.1.1.7, AChE). The enzyme activity was measured in 0.1 M phosphate buffer (pH 7.4) at 10 and 37 degrees C with acetylthiocholine (ATCh) as the substrate. The obtained enzyme/inhibitor dissociation constants were between 0.05 and 0.5 mM at 10 degrees C and between 0.2 and 0.6 mM at 37 degrees C. At both temperatures compounds III and IV had higher affinities for the enzyme than compounds I and II and this difference was more pronounced at 10 than at 37 degrees C. The carbamates II and IV were also progressive AChE inhibitors. For compound II the rate constants of inhibition were 6300 and 2020 M(-1) min(-1) at 37 and 10 degrees C, respectively. Compound IV was a very weak carbamoylating agent with rate constants of inhibition of 100 and 63 M(-1) min(-1) at 37 and 10 degrees C, respectively. The oxime group in compounds III and IV hydrolyzed ATCh at rates of 23 and 3.2 M(-1) min(-1) at 37 and 10 degrees C, respectively.
ESTHER : Reiner_1999_Chem.Biol.Interact_119-120_173
PubMedSearch : Reiner_1999_Chem.Biol.Interact_119-120_173
PubMedID: 10421451

Title : Paraoxonase and arylesterase activities in the serum of two hyperlipoproteinaemic patients after repeated extracorporal lipid precipitation - Reiner_1999_Chem.Biol.Interact_119-120_405
Author(s) : Reiner E , Svedruzic D , Simeon-Rudolf V , Lipovac V , Gavella M , Mrzljak V
Ref : Chemico-Biological Interactions , 119-120 :405 , 1999
Abstract : The effect of heparin-induced extracorporal lipid precipitation (HELP) on the activities of paraoxonase (EC 3.1.8.1) and arylesterase (EC 3.1.1.2) was studied in serum of a patient with hyperlipoproteinaemia (A) and of a patient with non-insulin dependent diabetes mellitus and hyperlipoproteinaemia (B). The enzyme activities were measured spectrophotometrically (Tris-HCl buffer, pH 7.4, 37 degrees C) with paraoxon and phenylacetate as substrates of paraoxonase and arylesterase, respectively. Both patients underwent HELP applications once a week over a period of 7 weeks. Over that period no overall change was observed either in enzyme activities or in the lipid and protein content of the sera. However, each HELP session caused an immediate decrease of EDTA-insensitive arylesterase activity (on average 56% in A and 42% in B), while EDTA-sensitive arylesterase remained almost unaltered. Paraoxonase remained unchanged in A, but decreased in B (approximately 60%). Of the atherogenic lipoprotein parameters, the most pronounced decrease was found in VLDL-cholesterol and in triglycerides (on average 45% in A and 32% in B), while the anti-atherogenic HDL-cholesterol decreased < 10%. Possible implications of the effect of HELP on the enzyme activities studied remain to be explained.
ESTHER : Reiner_1999_Chem.Biol.Interact_119-120_405
PubMedSearch : Reiner_1999_Chem.Biol.Interact_119-120_405
PubMedID: 10421477

Title : Catalytic parameters for the hydrolysis of butyrylthiocholine by human serum butyrylcholinesterase variants - Simeon-Rudolf_1999_Chem.Biol.Interact_119-120_165
Author(s) : Simeon-Rudolf V , Reiner E , Evans RT , George PM , Potter HC
Ref : Chemico-Biological Interactions , 119-120 :165 , 1999
Abstract : Catalysed hydrolysis of butyrylthiocholine (BTCh) by the usual (UU), fluoride-resistant (FS), AK, AJ and atypical (AA) human serum butyrylcholinesterase (EC 3.1.1.8) variants was measured in phosphate buffer pH 7.4 at 25 degrees C. pS-curves for all phenotypes were S-shaped; the activities rose to a plateau with increasing substrate concentration except at 100 mM where there was a small decrease. To obtain the catalytic constants, three equations were applied: Michaelis-Menten equation (Eq. 1), Hill equation (Eq. 2) and an equation which assumes simultaneous binding of the substrate to the catalytic site and to a peripheral site on the enzyme (Eq. 3). Over a range from 0.01 to 50 mM BTCh, the activity versus substrate concentration relationship deviated from Michaelis-Menten kinetics (Eq. 1) while data fitted well with Eqs. 2 and 3. The Michaelis-Menten equation was applied separately to two BTCh concentration ranges: the corresponding Km constants for the UU, FS, AK, AJ and AA phenotypes ranged from 0.1 to 0.2 mM (at 0.01-1.0 mM BTCh) and from 0.3 to 2.0 mM (at 1.0-50 mM BTCh). Hill coefficients (nH) calculated from Eq. 2 were similar for all phenotypes (nH approximately 0.5). The dissociation constants K1 and K2 calculated from Eq. 3 for two sites on the enzyme fell between 0.02 and 0.12 mM (K1) and 0.89 and 4.9 mM (K2) for the five phenotypes. Experimental data support the assumption that the phenotypes studied have two substrate binding sites.
ESTHER : Simeon-Rudolf_1999_Chem.Biol.Interact_119-120_165
PubMedSearch : Simeon-Rudolf_1999_Chem.Biol.Interact_119-120_165
PubMedID: 10421450

Title : Quinuclidinium-imidazolium compounds: synthesis, mode of interaction with acetylcholinesterase and effect upon Soman intoxicated mice - Simeon-Rudolf_1998_Arch.Toxicol_72_289
Author(s) : Simeon-Rudolf V , Reiner E , Skrinjaric-Spoljar M , Radic B , Lucic A , Primozic I , Tomic S
Ref : Archives of Toxicology , 72 :289 , 1998
Abstract : Four compounds were prepared: 3-oxo-1-methylquinuclidinium iodide (I), 2-hydroxyiminomethyl-1,3-dimethylimidazolium iodide (II) and two conjugates of I and II linked by -(CH2)3- (III) and -CH2-O-CH2- (IV). The aim was to evaluate separately the properties of I and II as opposed to III and IV, which contain both moieties in the same molecule. All four compounds were reversible inhibitors of acetylcholinesterase (AChE; EC 3.1.1.7). The enzyme/inhibitor dissociation constants for the catalytic site ranged from 0.073 mM (II) to 1.6 mM (I). The dissociation constant of I for the allosteric (substrate inhibition) site was 4.8 mM. Possible binding of the other compounds to the allosteric site could not be measured because II, III and IV reacted with the substrate acetylthiocholine (ATCh) and at high ATCh concentrations the non-enzymic reaction interfered with the enzymic hydrolysis of ATCh. The rate constants for the non-enzymic ATCh hydrolysis were between 23 and 37 l/mol per min. All four compounds protected AChE against phosphorylation by Soman and VX. The protective index (PI) of I (calculated from binding of I to both, catalytic and allosteric sites in AChE) agreed with the measured PI; this confirms that allosteric binding contributes to the decrease of phosphorylation rates. The PI values obtained with III and IV were higher than those predicted by the assumption of their binding to the AChE catalytic site only. The toxicity (i.p. LD50) of compounds I, II, III and IV for mice was 0.21, 0.68, 0.49 and 0.77 mmol/kg body wt. respectively. All four compounds protected mice against Soman when given (i.p.) together with atropine 1 min after Soman (s.c.). One-quarter of the LD50 dose fully protected mice (survival of all animals) against 2.52 (IV), 2.00 (I and III) and 1.58 (II) LD50 doses of Soman.
ESTHER : Simeon-Rudolf_1998_Arch.Toxicol_72_289
PubMedSearch : Simeon-Rudolf_1998_Arch.Toxicol_72_289
PubMedID: 9630015

Title : Inhibition of Acetylcholinesterase (ACHE\; E.C. 3.1.1.7) and Butyrylcholinesterase (BCHE\; E.C. 3.1.1.8) by Terbutaline -
Author(s) : Kovarik Z , Radic Z , Skrinjaric-Spoljar M , Reiner E , Simeon-Rudolf V
Ref : In: Structure and Function of Cholinesterases and Related Proteins - Proceedings of Sixth International Meeting on Cholinesterases , (Doctor, B.P., Taylor, P., Quinn, D.M., Rotundo, R.L., Gentry, M.K. Eds) Plenum Publishing Corp. :243 , 1998
PubMedID:

Title : Catalytic properties and distribution profiles of paraoxonase and cholinesterase phenotypes in human sera. - Reiner_1995_Toxicol.Lett_83_447
Author(s) : Reiner E , Simeon-Rudolf V , Skrinjaric-Spoljar M
Ref : Toxicology Letters , 83 :447 , 1995
Abstract : Paraoxonase activities (322 healthy subjects) measured in the absence of ethylenediaminetetraacetic acid (EDTA) had a polymodal distribution profile with 60% of the subjects in the low activity mode; the activity measured in the presence of EDTA had a unimodal skewed distribution. Cholinesterase (ChE) activities (365 healthy subjects) had a unimodal, slightly skewed distribution. Patients with dementia (74) and patients with hyperlipidaemia (159) had different median paraoxonase and ChE activities than healthy subjects and all activity profiles had a higher skewness. The ChE variants usual (UU), fluoride resistant (FS) and atypical (AA) had the same affinity for the studied charged and uncharged ligands. The variants differed in rates of inhibition by the charged organophosphates and carbamates.
ESTHER : Reiner_1995_Toxicol.Lett_83_447
PubMedSearch : Reiner_1995_Toxicol.Lett_83_447
PubMedID: 8597092

Title : Catalytic Properties of Human Serum Cholinesterase Phenotypes in their Reaction with Substrates and Inhibitors -
Author(s) : Simeon-Rudolf V , Skrinjaric-Spoljar M , Reiner E
Ref : In Enzyme of the Cholinesterase Family - Proceedings of Fifth International Meeting on Cholinesterases , (Quinn, D.M., Balasubramanian, A.S., Doctor, B.P., Taylor, P., Eds) Plenum Publishing Corp. :225 , 1995
PubMedID:

Title : Recommendations of the IUBMB Nomenclature Committee: comments concerning classification and nomenclature of esterases hydrolysing organophosphorus compounds -
Author(s) : Reiner E
Ref : Chemico-Biological Interactions , 87 :15 , 1993
PubMedID: 8343973

Title : Differentiation of esterases reacting with organophosphorus compounds - Reiner_1993_Chem.Biol.Interact_87_77
Author(s) : Reiner E , Pavkovic E , Radic Z , Simeon-Rudolf V
Ref : Chemico-Biological Interactions , 87 :77 , 1993
Abstract : The hydrolysis of paraoxon (POX), phenylacetate (PA) and beta-naphthylacetate (BNA) was studied in human serum. Based upon correlations between enzyme activities, upon reversible inhibition by EDTA and upon progressive inhibition by iso-OMPA, tabun, eserine and bis-4 nitrophenylphosphate, the following conclusions were drawn about the number and specificity of enzymes involved in the hydrolysis. Two paraxonases hydrolyse paraoxon: one sensitive and the other insensitive to EDTA. The EDTA-sensitive paraoxonase also hydrolysed BNA. The EDTA-insensitive hydrolysis of BNA and PA was attributed to a serine esterase. The EDTA-sensitive hydrolysis of PA is probably due to more than one enzyme, which might be an arylesterase and a carboxylesterase.
ESTHER : Reiner_1993_Chem.Biol.Interact_87_77
PubMedSearch : Reiner_1993_Chem.Biol.Interact_87_77
PubMedID: 8393750

Title : Interaction of imidazolium and pyridinium dioximes with human erythrocyte acetylcholinesterase - Franciskovic_1993_Chem.Biol.Interact_87_323
Author(s) : Franciskovic L , Spoljar MS , Reiner E
Ref : Chemico-Biological Interactions , 87 :323 , 1993
Abstract : Two pyridinium and two imidazolium dioximes were tested as reversible inhibitors of human erythrocyte acetylcholinesterase (AChE), as protectors of the enzyme against phosphorylation and as reactivators of the phosphorylated AChE. All four dioximes reversibly inhibited AChE, protected the enzyme against phosphorylation by soman and tabun and reactivated AChE after phosphorylation by sarin, VX and tabun. From the experimental results the enzyme/dioxime dissociation constants were evaluated for the catalytically active enzyme and for phosphorylated enzyme. The evaluation constants have shown that all four dioximes have about the same affinity for the catalytically active as for the phosphylated AChE. Obtained results also indicate that imidazolium dioximes probably bind only to the allosteric, while pyridinium dioximes bind to both, the catalytic and the allosteric site of the enzyme.
ESTHER : Franciskovic_1993_Chem.Biol.Interact_87_323
PubMedSearch : Franciskovic_1993_Chem.Biol.Interact_87_323
PubMedID: 8343989

Title : A field-test for detecting organophosphorus compounds in water - Reiner_1993_Arh.Hig.Rada.Toksikol_44_159
Author(s) : Reiner E , Simeon V , Simaga S , Cizl S , Jelicic D , Sumanovic V , Batinic D
Ref : Arh Hig Rada Toksikol , 44 :159 , 1993
Abstract : An enzyme test has been worked out for detecting organophosphorus compounds in water. The test is based on the inhibition of cholinesterase. The detection limits for the "nerve gases" are (microgram/L): Soman 0.12, VX 5.9, Sarin 9.9 and Tabun 26. The detection limit for the organophosphorus pesticide dichlorvos is 50 micrograms/L.
ESTHER : Reiner_1993_Arh.Hig.Rada.Toksikol_44_159
PubMedSearch : Reiner_1993_Arh.Hig.Rada.Toksikol_44_159
PubMedID: 8240025

Title : Hydrolysis of some organophosphorus dichlorophenyl esters by hen brain homogenates and rabbit serum compared with hydrolysis of paraoxon - Reiner_1993_Chem.Biol.Interact_87_127
Author(s) : Reiner E , Johnson MK , Jokanovic M
Ref : Chemico-Biological Interactions , 87 :127 , 1993
Abstract : The hydrolysis of four organophosphorus dichlorophenyl esters and of paraoxon was studied in hen brain homogenates and in rabbit serum. All compounds were hydrolysed by both preparations, but the rates were different in the two preparations. EDTA inhibited the hydrolysis almost completely in rabbit serum, but had only a small effect on the hydrolysis in hen brain homogenates.
ESTHER : Reiner_1993_Chem.Biol.Interact_87_127
PubMedSearch : Reiner_1993_Chem.Biol.Interact_87_127
PubMedID: 8393734

Title : Serum paraoxonase and cholinesterase activities in individuals with lipid and glucose metabolism disorders - Pavkovic_1993_Chem.Biol.Interact_87_179
Author(s) : Pavkovic E , Simeon-Rudolf V , Reiner E , Sucic M , Lipovac V
Ref : Chemico-Biological Interactions , 87 :179 , 1993
Abstract : In patients with hyperlipaemia, serum paraoxonase activities were polymodally distributed with 75% individuals in the low activity mode. In the same patients the distribution of serum cholinesterase activities was unimodal, but asymmetrical. Patients with impaired glucose tolerance or non-insulin-dependent diabetes mellitus had slightly higher cholinesterase activities than patients with hyperlipaemia only.
ESTHER : Pavkovic_1993_Chem.Biol.Interact_87_179
PubMedSearch : Pavkovic_1993_Chem.Biol.Interact_87_179
PubMedID: 8393741

Title : Dialkylphosphorus metabolites in the urine and activities of esterases in the serum as biochemical indices for human absorption of organophosphorus pesticides - Drevenkar_1991_Arch.Environ.Contam.Toxicol_20_417
Author(s) : Drevenkar V , Radic Z , Vasilic Z , Reiner E
Ref : Archives of Environmental Contamination & Toxicology , 20 :417 , 1991
Abstract : Ninety-seven agricultural workers were monitored for absorption of the organophosphorus pesticides methidathion, vamidothion, and azinphos-methyl, which were sprayed in an orchard during two seasons. Low levels of only one dialkylphosphorus metabolite (dimethyl phosphorothioate) were found in only eight workers in pre-exposure urine samples. More than one dialkylphosphorus metabolite was detected in almost all exposed individuals in after-exposure urine samples. The highest concentrations were measured after exposure to azinphos-methyl; the median concentrations of dimethyl phosphorodithioate and dimethyl phosphorothioate were 0.92 and 0.78 nmol/mg creatinine with a concentration range up to 14.3 and 53.7, respectively. Three diethylphosphorus metabolites were also detected in some samples, but at lower concentrations. Cholinesterase activities were decreased (31-48%) in the serum of 12 workers; four of those workers had no dialkylphosphorus metabolites in the urine. Paraoxonase and arylesterase activities in the serum were unaffected by the absorption of pesticides, and there was no correlation between the activities of these esterases and the metabolite concentrations in the urine. This study confirmed that dialkylphosphorus metabolites in the urine are a more sensitive index of absorption than cholinesterase inhibition in the serum but lack of correlation between cholinesterase inhibition and metabolite concentration indicates that both parameters should be monitored.
ESTHER : Drevenkar_1991_Arch.Environ.Contam.Toxicol_20_417
PubMedSearch : Drevenkar_1991_Arch.Environ.Contam.Toxicol_20_417
PubMedID: 1650168

Title : Role of the peripheral anionic site on acetylcholinesterase: inhibition by substrates and coumarin derivatives - Radic_1991_Mol.Pharmacol_39_98
Author(s) : Radic Z , Reiner E , Taylor P
Ref : Molecular Pharmacology , 39 :98 , 1991
Abstract : Propidium has been demonstrated in previous studies to be a selective ligand for the peripheral anionic site on acetylcholinesterase (EC 3.1.1.7). Its association with this site can be advantageously monitored by direct fluorescent titration. We have measured the ability of acetylcholine, acetylthiocholine, haloxon [di-(2-chloroethyl)3-chloro-4-methylcoumarin-7-ylphosphate] , and a coumarin derivative (3-chloro-7-hydroxy-4-methylcoumarin) to dissociate propidium from the peripheral anionic site of Torpedo californica acetylcholinesterase. Measurements were made by back-titration of propidium after complete inhibition of the active center with diisopropylfluorophosphate. Both acetylcholine and acetylthiocholine show substrate inhibition at high substrate concentrations. The concentrations required for occupation of the peripheral site, as ascertained by competition with propidium, correlated well with the concentration dependence for the kinetics of substrate inhibition. These observations are consistent with substrate inhibition being due to binding of acetylcholine or acetylthiocholine at a peripheral anionic site. Displacement of propidium by haloxon and coumarin indicated that these inhibitors also bind to the peripheral anionic site. The dissociation constants ascertained from peripheral site occupation are in agreement with the constants obtained from inhibition kinetics. Evidence is presented that competition with propidium obtained by direct fluorescence titrations, when combined with inhibition kinetics, provides a more reliable means for ascertaining site selectivity of various inhibitors than does a kinetic analysis alone.
ESTHER : Radic_1991_Mol.Pharmacol_39_98
PubMedSearch : Radic_1991_Mol.Pharmacol_39_98
PubMedID: 1987454

Title : Mechanism of Substrate Inhibition of Acetylcholinesterase -
Author(s) : Reiner E , Aldridge WN , Simeon-Rudolf V , Radic Z , Taylor P
Ref : In: Cholinesterases: Structure, Function, Mechanism, Genetics, and Cell Biology , (Massoulie J, Barnard EA, Chatonnet A, Bacou F, Doctor BP, Quinn DM) American Chemical Society, Washington, DC :227 , 1991
PubMedID:

Title : Poster: Human serum esterases: differentiation of EDTA-insensitive enzymes -
Author(s) : Radic Z , Pavkovic E , Reiner E
Ref : In: Cholinesterases: Structure, Function, Mechanism, Genetics, and Cell Biology , (Massoulie J, Barnard EA, Chatonnet A, Bacou F, Doctor BP, Quinn DM) American Chemical Society, Washington, DC :288 , 1991
PubMedID:

Title : Inhibition of serum cholinesterase by trialkylphosphorothiolates - Franciskovic_1989_Arch.Toxicol_63_489
Author(s) : Franciskovic L , Radic Z , Reiner E
Ref : Archives of Toxicology , 63 :489 , 1989
Abstract : The kinetics of inhibition of horse serum cholinesterase (EC 3.1.1.8) by six trialkylphosphorothiolates was studies (25 degrees C, pH 7.4). The compounds were : OOS-trimethylphosphorothiolate (OOS-Me), OSS-trimethylphosphorodithiolate (OSS-Me), SSS-trimethylphosphorotrithiolate (SSS-Me) and their corresponding ethyl analogues (OOS-Et, OSS-Et, SSS-Et). The second order rate constants of inhibition ranged from 7.2 to 2128 mol-1 1 min-1, of inhibition ranged from 7.2 to 2128 mol-1 1 min-1, and the enzyme/inhibitor dissociation constants from 0.079 to 1.5 mM. The ethyl esters were better inhibitors than their methyl analogues and the OSS-compounds were better inhibitors than the OOS- or SSS-compounds. The same structure-activity relationship is known to hold for the reaction of the compounds with acetylcholinesterase (EC 3.1.1.7).
ESTHER : Franciskovic_1989_Arch.Toxicol_63_489
PubMedSearch : Franciskovic_1989_Arch.Toxicol_63_489
PubMedID: 2619563

Title : Cholinesterases in rabbit serum - Simeon_1988_Gen.Pharmacol_19_849
Author(s) : Simeon-Rudolf V , Reiner E , Skrinjaric-Spoljar M , Krauthacker B
Ref : General Pharmacology , 19 :849 , 1988
Abstract : 1. Rabbit serum was shown to contain two cholinesterases which hydrolysed acetylthiocholine and butyrylthiocholine and one cholinesterase which hydrolysed only butyrylthiocholine. 2. The three enzymes were identified by the kinetics of heat inactivation and kinetics of phosphorylation by the organophosphate VX. 3. Using selective inhibitors (iso-OMPA, eserine, BNPP and BW-284C51) it was shown that the hydrolysis of acetylthiocholine and butyrylthiocholine in untreated native serum had properties of acetylcholinesterase (EC 3.1.1.7), butyrylcholinesterase (EC 3.1.1.8) and also some properties of carboxylesterase (EC 3.1.1.1). 4. Separation of proteins (on PAA-gels) in untreated native serum gave four bands with acetylthiocholine and three with butyrylthiocholine. 5. The two cholinesterases hydrolysing both substrates corresponded to the slow moving bands on the gel. 6. The fastest moving band hydrolysing only butyrylthiocholine could be attributed to the cholinesterase least sensitive to VX.
ESTHER : Simeon_1988_Gen.Pharmacol_19_849
PubMedSearch : Simeon_1988_Gen.Pharmacol_19_849
PubMedID: 3229626

Title : Kinetics of heat inactivation of phenyl valerate hydrolases from hen and rat brain - Reiner_1987_Biochem.Pharmacol_36_3181
Author(s) : Reiner E , Davis CS , Schwab BW , Schopfer LM , Richardson RJ
Ref : Biochemical Pharmacology , 36 :3181 , 1987
Abstract : Heat inactivation was studied at 45, 50, 55, and 60 degrees for all of the phenyl valerate hydrolases (PVase), including neurotoxic esterase (NTE) and inhibitor-resistant esterase (IRE), in homogenates of hen or rat brain or in preparations of hen brain microsomal membranes. Hen and rat brain homogenates were prepared in buffer (50 mM Tris/0.20 mM EDTA, pH 8.00, at 25 degrees). Hen brain microsomes were suspended either in buffer or in aqueous dimethyl sulfoxide (DMSO, 40%, w/v), or solubilized either in aqueous Triton X-100 (0.10%, w/v) or in 40% (w/v) DMSO. Enzyme activities were measured at 37 degrees using phenyl valerate as substrate. Each enzyme activity in all of the preparations exhibited biphasic heat inactivation kinetics. Apparent rate constants were calculated for the fast (kf) and slow (ks) reactions, along with the relative amounts of activity in each component (Af, As) expressed as percentages of the total activity. For a given preparation and temperature, respective values of kf or ks were similar for PVase, NTE, and IRE, with a mean kf/ks ratio of 52 across all preparations. Af and As were a function of temperature. Mean values of the apparent activation energies (Ea) for all activities and preparations were 44 and 25 kcal/mol for the fast and slow inactivation reactions respectively. These results indicate that all phenyl valerate hydrolases in hen and rat brain undergo a common heat-induced structural change leading to loss of enzymic activity.
ESTHER : Reiner_1987_Biochem.Pharmacol_36_3181
PubMedSearch : Reiner_1987_Biochem.Pharmacol_36_3181
PubMedID: 3663234

Title : An enzyme test for determining isomalathion impurities in water-dispersible powders of malathion - Reiner_1986_Bull.World.Health.Organ_64_397
Author(s) : Reiner E , Radic Z
Ref : Bulletin of the World Health Organization , 64 :397 , 1986
Abstract : An enzyme test for determining isomalathion (O,S-dimethyl-S-(1,2-dicarbethoxyethyl) phosphorodithioate) impurities in water-dispersible powders of malathion (WDP malathion) is described. The test is based on inhibition of acetylcholinesterase (EC 3.1.1.7) by isomalathion extracted from WDP malathion. The lower limit of detection of the test is 0.01% (w/w) isomalathion. For 18 samples of WDP malathion there was good correlation between the levels of isomalathion found using the enzyme test and those obtained by thin-layer chromatography.
ESTHER : Reiner_1986_Bull.World.Health.Organ_64_397
PubMedSearch : Reiner_1986_Bull.World.Health.Organ_64_397
PubMedID: 3490319

Title : Sites for reversible binding of acylating inhibitors to acetylcholinesterase evaluated from kinetic studies -
Author(s) : Reiner E
Ref : In: Cholinesterases, fundamental and applied aspects : proceedings of the Second International Meeting on Cholinesterases , (Brzin M, Barnard EA, Sket D, Eds) De Gruyter :37 , 1984
PubMedID:

Title : Binding sites on acetylcholinesterase for reversible ligands and phosphorylating agents. A theoretical model tested on haloxon and phosphostigmine - Radic_1984_Biochem.Pharmacol_33_671
Author(s) : Radic Z , Reiner E , Simeon-Rudolf V
Ref : Biochemical Pharmacology , 33 :671 , 1984
Abstract : The reaction of acetylcholinesterase (EC 3.1.1.7; human erythrocytes) with phosphostigmine, haloxon and VX was studied, and the effect of three reversible ligands (TMA, edrophonium, coumarin) and of acetylthiocholine upon the time-dependent and time-independent (reversible) inhibition by the organophosphates was evaluated. The three ligands and acetylthiocholine decreased the second-order rate constant of phosphorylation by a factor proportional to the enzyme-ligand dissociation constant, or to both Km and Kss (Michaelis constant and the substrate-inhibition constant for acetylthiocholine) irrespective of the organophosphate. However, the time-independent inhibitions by phosphostigmine and haloxon were differently affected. Acetylthiocholine affected the time-independent inhibition by phosphostigmine by a factor proportional to Km, and that by haloxon by a factor proportional to Kss. Coumarin had no effect on the time-independent inhibition by phosphostigmine, while TMA and edrophonium displaced phosphostigmine from its complex. Coumarin displaced haloxon from its complex with the enzyme, while TMA and edrophonium had no effect. We conclude that phosphostigmine and haloxon bind reversibly to different sites on the enzyme and the experiments agree with a theoretical model that haloxon binds reversibly to a peripheral site on acetylcholinesterase, and phosphostigmine to the catalytic site.
ESTHER : Radic_1984_Biochem.Pharmacol_33_671
PubMedSearch : Radic_1984_Biochem.Pharmacol_33_671
PubMedID: 6704184

Title : Introduction to session I. Chemistry and catalytic activity of cholinesterase -
Author(s) : Reiner E
Ref : In: Cholinesterases, fundamental and applied aspects : proceedings of the Second International Meeting on Cholinesterases , (Brzin M, Barnard EA, Sket D, Eds) De Gruyter :3 , 1984
PubMedID:

Title : The identification and characterization of two separate carboxylesterases in guinea-pig serum - Cain_1983_Biochem.J_215_91
Author(s) : Cain K , Reiner E , Williams DG
Ref : Biochemical Journal , 215 :91 , 1983
Abstract : The esterase activity of guinea-pig serum was investigated. A 3-fold purification was achieved by removing the serum albumin by Blue Sepharose CL-6B affinity chromatography. The partially purified enzyme preparation had carboxylesterase and cholinesterase activities of 1.0 and 0.22 mumol of substrate/min per mg of protein respectively. The esterases were labelled with [3H]di-isopropyl phosphorofluoridate (DiPF) and separated electrophoretically on sodium dodecyl sulphate/polyacrylamide gels. Two main labelled bands were detected: band I had Mr 80 000 and bound 18-19 pmol of [3H]DiPF/mg of protein, and band II had Mr 58 000 and bound 7 pmol of [3H]DiPF/mg of protein. Bis-p-nitrophenyl phosphate (a selective inhibitor of carboxylesterase) inhibited most of the labelling of bands I and II. The residual labelling (8%) of band I but not band II (4%) was removed by preincubation of partially purified enzyme preparation with neostigmine (a selective inhibitor of cholinesterase). Paraoxon totally prevented the [3H]DiPF labelling of the partially purified enzyme preparation. Isoelectrofocusing of [3H]DiPF-labelled and uninhibited partially purified enzyme preparation revealed that there were at least two separate carboxylesterases, which had pI3.9 and pI6.2, a cholinesterase enzyme (pI4.3) and an unidentified protein that reacts with [3H]DiPF and has a pI5.0. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of these enzymes showed that the carboxylesterase enzymes at pI3.9 and pI6.2 corresponded to the 80 000-Mr subunit (band I) and 58 000-Mr subunit (band II). The cholinesterase enzyme was also composed of 80 000-Mr subunits (i.e. the residual labelling in band I after bis-p-nitrophenyl phosphate treatment). The unidentified protein at pI5.0 corresponded to the residual labelling in band II (Mr 58 000), which was insensitive to neostigmine and bis-p-nitrophenyl phosphate. These studies show that the carboxylesterase activity of guinea-pig serum is the result of at least two separate and distinct enzymes.
ESTHER : Cain_1983_Biochem.J_215_91
PubMedSearch : Cain_1983_Biochem.J_215_91
PubMedID: 6626182

Title : Dimethylphosphorothioates. Reaction with malathion and effect on malathion toxicity - Verschoyle_1982_Arch.Toxicol_49_293
Author(s) : Verschoyle RD , Reiner E , Bailey E , Aldridge WN
Ref : Archives of Toxicology , 49 :293 , 1982
Abstract : Five dimethylphosphorothioates were tested for their toxicity to rats, potentiation of malathion toxicity in rats, inhibition of carboxylesterase in vitro, and reaction with malathion in vitro. The compounds were: potassium salts of (CH3S)2P(O)O-(I), (CH3O)(CH3S)P(O)S-(II), (CH3O)2P(O)S-(III), (CH3O)2P(S)S-(IV), and (CH3O)(CH3S)P(O)O-(V). The dimethylphosphorothioates are not toxic to rats (up to 1 g/kg, orally), they do not potentiate malathion toxicity in rats, and do not inhibit carboxylesterase activity in vitro (up to 1 mM concentrations). However, when the S-acid diesters (II, III, IV) are incubated with malathion for serveral days at room temperature or for several hours at 50 degrees C they become methylated forming the trimethylphosphorothioates OSS-trimethyl phosphorodithioate, OOS-trimethyl phosphorothioate and OOS-trimethyl phosphorodithioate respectively, which potentiate malathion toxicity. Furthermore, these same acid diesters increase the rate of isomerization of malathion into OS-dimethyl-S-(1,2-dicarbethoxyethyl) phosphorodithioate (isomalathion) particularly, diester IV. The formation of the trimethylphosphorothioates and isomalathion from the interaction of the S-acid diesters with malathion was determined by thin layer chromatography (TLC), gas chromatography and mass spectrometry and could be detected by in vitro inhibition of carboxylesterase. TLC methods can detect 1 mg of the trimethylphosphorothioates and isomalathion per gram malathion.
ESTHER : Verschoyle_1982_Arch.Toxicol_49_293
PubMedSearch : Verschoyle_1982_Arch.Toxicol_49_293
PubMedID: 7092568

Title : Interaction of some trialkyl phosphorothiolates with acetylcholinesterase. Characterization of inhibition, aging and reactivation - Clothier_1981_Biochim.Biophys.Acta_660_306
Author(s) : Clothier B , Johnson MK , Reiner E
Ref : Biochimica & Biophysica Acta , 660 :306 , 1981
Abstract : The reaction of bovine erythrocyte acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) with a set of structurally related phosphorothiolates was studied in order to investigate the properties of the phosphorylated enzymes and to identify the leaving group. OOS- and OOS-trimethyl phosphorothiolates and their triethyl analogues inhibit acetylcholinesterase reversibly and by progressive inhibition, and the phosphorylated enzymes undergo both spontaneous reactivation and aging. For each compound the enzyme-inhibitor dissociation constant, and the rate constants for inhibition (ka), reactivation and aging have been derived. The OOS-compounds are more potent inhibitors than the OOS-compounds, and the derived inhibited enzymes reactivate and age faster. By comparing reactivation and aging rate constants with those obtained from phosphorylated enzymes of known structure it was concluded that the leaving group of during phosphorylation is the S-alkyl. SSS-trimethyl and -triethyl phosphorothiolates also form reversible complexes and inhibit the enzyme progressively. With these inhibitors the phosphorylated enzymes did not reactivate either spontaneously or in response to oximes under conditions successful for the other inhibitors. The ka values (37 degrees C, pH 7.4) range from 30 M-1 X min-1 (OOS-trimethyl phosphorothiolate) to 6.7 X 10(3) M-1 X min-1 (OOS-triethyl phosphorothiolate) as compared to 1.25 X 10(5) M-1 X min-1 determined for isomalathion (O, S-dimethyl S-(1,2-dicarbethoxyethyl)-phoshporodithioate), which was used as one of the reference compounds. If the inhibitory potency of the trialkyl phosphorothiolates is calculated from measurements made after a fixed preincubation time the results in ka values will be misleading.
ESTHER : Clothier_1981_Biochim.Biophys.Acta_660_306
PubMedSearch : Clothier_1981_Biochim.Biophys.Acta_660_306
PubMedID: 7284405

Title : DDT residues in samples of human milk, and in mothers' and cord blood serum, in a continental town in Croatia (Yugoslavia) - Krauthacker_1980_Int.Arch.Occup.Environ.Health_46_267
Author(s) : Krauthacker B , Alebic-Kolbah T , Buntic A , Tkalcevic B , Reiner E
Ref : Int Arch Occup Environ Health , 46 :267 , 1980
Abstract : Concentrations of p,p'-DDE, p,p'-DDD, and p,p'-DDT were determined in 34 samples of human milk obtained 3-5 days after delivery and in 37 samples obtained at later times of lactation (up to 55 weeks). All samples contained p,p'-DDE, but only several contained p,p'-DDD and p,p'-DDT. The concentrations of p,p'-DDE were 31 microgram/l in the beginning of lactation and 53 microgram/l at later time intervals. The concentration ranges in both groups overlap almost completely and the difference in the mean values is not significant. Serum samples from 35 mothers and cord blood were also analyzed. All samples contained p,p'-DDE, the concentrations being 18 microgram/l and 6.8 microgram/l in the mothers' and cord blood serum, respectively. Serum samples of 24 non-pregnant women contained the same amount of p,p'-DDE (20 microgram/l) as mothers' sera. All samples were collected in a continental town of Croatia (Yugoslavia) between 1977 and 1979. The concentrations of DDT residues were determined by gas chromatography, and two methods for extraction from milk were used and compared.
ESTHER : Krauthacker_1980_Int.Arch.Occup.Environ.Health_46_267
PubMedSearch : Krauthacker_1980_Int.Arch.Occup.Environ.Health_46_267
PubMedID: 7450891

Title : Regeneration of cholinesterase activities in humans and rats after inhibition by O,O-dimethyl-2,2-dichlorovinyl phosphate -
Author(s) : Reiner E , Plestina R
Ref : Toxicology & Applied Pharmacology , 49 :451 , 1979
PubMedID: 473212

Title : Kinetic properties of the cholinesterase in Metastrongylus apri (Nematoda): substrate hydrolysis and reaction with organophosphorus compounds -
Author(s) : Reiner E , Skrinjaric-Spoljar M , Kralj M , Krvavica S
Ref : Comparative Biochemistry & Physiology C Pharmacol Toxicol , 60 :155 , 1978
PubMedID: 28886

Title : Competition between substrates for acetylcholinesterase and cholinesterase - Reiner_1977_Biochim.Biophys.Acta_480_137
Author(s) : Reiner E , Simeon-Rudolf V
Ref : Biochimica & Biophysica Acta , 480 :137 , 1977
Abstract : The kinetics of competition of pairs of two substrates for bovine erythrocyte acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) and horse serum cholinesterase (acylcholine acyl-hydrolase, EC 3.1.1.8) was studied so that the hydrolysis of only one substrate was measured at a time. The substrates were acetylthiocholine, were used as competiting substrates i.e. inhibitors. The substrate inhibition constants (Kss) and Michaelis constants for the reaction of a single substrate were also determined. It was concluded that the substrate inhibition site in the enzyme does not show up in the competition between two substrates.
ESTHER : Reiner_1977_Biochim.Biophys.Acta_480_137
PubMedSearch : Reiner_1977_Biochim.Biophys.Acta_480_137
PubMedID: 831831

Title : Mechanism of inhibition in vitro of mammalian acetylcholinesterase and cholinesterase in solutions of 0,0-dimethyl 2,2,2-trichloro-1-hydroxyethyl phosphonate (Trichlorphon) -
Author(s) : Reiner E , Krauthacker B , Simeon-Rudolf V , Skrinjaric-Spoljar M
Ref : Biochemical Pharmacology , 24 :717 , 1975
PubMedID: 235931

Title : Kinetic study of the effect of substrates on reversible inhibition of cholinestemse and acetylcholinesterase by two coumarin derivatives -
Author(s) : Reiner E , Simeon-Rudolf V
Ref : Croatica Chemica Acta , 47 :321 , 1975
PubMedID:

Title : General discussion on models for the ligand binding sites of cholinesterase -
Author(s) : Reiner E , Aldridge WN , Hopff WH , Taylor P , Krupka RM , Rosenberry TL , Augustinsson KB , Mooser G , O'Brien RD , Brodbeck U , Massoulie J , Maricic S , Eldefrawi ME , Silman I
Ref : Croatica Chemica Acta , 47 :499 , 1975
PubMedID:

Title : Effect of temperature on the activity of human blood cholinesterases -
Author(s) : Reiner E , Buntic A , Trdak M , Simeon-Rudolf V
Ref : Archives of Toxicology , 32 :347 , 1974
PubMedID: 4480035

Title : Effect of sample storage on human blood cholinesterase activity after inhibition by carbamates - Wilhelm_1973_Bull.World.Health.Organ_48_235
Author(s) : Wilhelm K , Reiner E
Ref : Bulletin of the World Health Organization , 48 :235 , 1973
Abstract : During an operational field trial with propoxur it was observed that the inhibition of whole blood cholinesterase was greater when samples were stored before the assay. Since measurement of cholinesterase activity is not always possible immediately after sampling, the effects of different storage conditions were evaluated. Human blood cholinesterases were inhibited in vitro by methylcarbamates and stored at different pH values, temperatures, and sample dilutions. The results showed that the degree of cholinesterase inhibition does not change if samples are diluted 300-fold with buffer at pH 5.0 at 4 degrees C and the enzyme activity measured within 4 hours after dilution. These conditions of storage were equally satisfactory for each of the three methylcarbamates studied and are therefore likely to apply to other carbamates as well.
ESTHER : Wilhelm_1973_Bull.World.Health.Organ_48_235
PubMedSearch : Wilhelm_1973_Bull.World.Health.Organ_48_235
PubMedID: 4541688

Title : Comparison of methods for measuring cholinesterase inhibition by carbamates -
Author(s) : Wilhelm K , Vandekar M , Reiner E
Ref : Bulletin of the World Health Organization , 48 :41 , 1973
PubMedID: 4541147

Title : Comparison between inhibition of acetylcholinesterase and cholinesterase by some N-methyl- and NN-dimethyl-carbamates -
Author(s) : Simeon-Rudolf V , Reiner E
Ref : Arhiv Za Higijenu Rada i Toksikologiju , 24 :199 , 1973
PubMedID: 4786699

Title : Effect of temperature and pH on carbamoylation and phosphorylation of serum cholinesterases. Theoretical interpretation of activation energies in complex reactions - Simeon_1972_Biochem.J_130_515
Author(s) : Simeon-Rudolf V , Reiner E , Vernon CA
Ref : Biochemical Journal , 130 :515 , 1972
Abstract : 1. The effect of temperature and pH was studied on the kinetics of inhibition of horse serum and human serum cholinesterase by four organophosphorus compounds and five carbamates. 2. For all compounds, and at each pH and temperature, the inhibition followed the kinetics of a bimolecular reaction with the inhibitor in excess, and with a negligible concentration of the Michaelis complex. 3. The second-order rate constants (k(a)) for inhibition of human serum cholinesterase by one organophosphate and one carbamate increased from 5 degrees to 40 degrees C with an apparent activation energy of 46kJ/mol (11kcal/mol). 4. The k(a) constant for inhibition of horse serum cholinesterase increased with temperature from 5 degrees to 30 degrees C, and then decreased from 30 degrees to 40 degrees C. The theoretical interpretation of such an unusual effect of temperature is derived. 5. The increase of k(a) with pH (human serum cholinesterase) followed the dissociation curve for a single group on the enzyme (pK7.5). 6. Rate constants for decarbamoylation (k(+3)) were determined, and the time-course of inhibition was calculated from the k(a) and k(+3) constants.
ESTHER : Simeon_1972_Biochem.J_130_515
PubMedSearch : Simeon_1972_Biochem.J_130_515
PubMedID: 4677141

Title : Spontaneous reactivation of phosphorylated and carbamylated cholinesterases -
Author(s) : Reiner E
Ref : Bulletin of the World Health Organization , 44 :109 , 1971
PubMedID: 5315341

Title : Acetylcholinesterase. Two types of inhibition by an organophosphorus compound: one the formation of phosphorylated enzyme and the other analogous to inhibition by substrate -
Author(s) : Aldridge WN , Reiner E
Ref : Biochemical Journal , 115 :147 , 1969
PubMedID: 5378376

Title : The inhibitory power of 2-isopropoxyphenyl-N-methyl- carbamate against serum cholinesterase of various individuels -
Author(s) : Reiner E , Simeon-Rudolf V
Ref : Archives of Toxicology , 23 :237 , 1968
PubMedID:

Title : Effect of pH on inhibition and spontaneous reactivation of acetylcholinesterase treated with esters of phosphorus acids and of carbamic acids -
Author(s) : Reiner E , Aldridge WN
Ref : Biochemical Journal , 105 :171 , 1967
PubMedID: 6070126

Title : The kinetics of inhibition of erythrocyte cholinesterase by monomethylcarbamates -
Author(s) : Reiner E , Simeon-Rudolf V
Ref : Biochemical Journal , 98 :501 , 1966
PubMedID: 5941343

Title : Occurrence of cholinesterase isoenzymes in horse serum -
Author(s) : Reiner E , Seuferth W , Hardegg W
Ref : Nature , 205 :1110 , 1965
PubMedID: 5889293

Title : Oxime reactivation of erythrocyte cholinesterase inhibited by ethyl p-nitrophenyl ethylphosphonate -
Author(s) : Reiner E
Ref : Biochemical Journal , 97 :710 , 1965
PubMedID: 5881660