Marcel V

References (11)

Title : A High Number of Mutations in Insect Acetylcholinesterase May Provide Insecticide Resistance - Villatte_2000_Pestic.Biochem.Physiol_67_95
Author(s) : Villatte F , Ziliani P , Marcel V , Menozzi P , Fournier D
Ref : Pesticide Biochemistry and Physiology , 67 :95 , 2000
Abstract : Many insect pest species have developed insecticide resistance through modifications of acetylcholinesterase. Seven mutations, issued from one nucleotide change, have been associated with resistance in natural populations of Drosophila and housefly (A. Mutero, M. Pralavorio, J. M. Bride, and D. Fournier, Resistance-associated point mutations in insecticide insensitive acetylcholinesterase, Proc. Natl. Acad Sci. USA91, 5922 (1994); A. L. Devonshire, F. J Byrne, G. D. Moores, and M. S. Williamson, Biochemical and molecular characterisation of insecticide-insensitive acetylcholinesterases in resistant insects, in -YStructure and function of cholinesterases and related proteins (B. P. Doctor, P. Taylor, D. M. Quinn, R. L. Rotundo, and M. K. Gentry, Eds.), pp. 491-496, Plenum Press, New York, 1998). In order to study the number of mutations which can lead to resistance, we first analyzed the effects of a set of amino acid replacements in the Drosophila acetylcholinesterase on inhibition by several carbamate and organophosphate insecticides. It appeared that most of the mutations led to a reduced sensitivity to insecticides. Second, we investigated the effect of mutations on substrate hydrolysis. We found that most of the variants retained sufficient levels of substrate hydrolysis. These data suggest that more mutations in acetylcholinesterase may be involved in organophosphate and carbamate resistance in addition to the previously known seven mutations.
ESTHER : Villatte_2000_Pestic.Biochem.Physiol_67_95
PubMedSearch : Villatte_2000_Pestic.Biochem.Physiol_67_95

Title : A method to estimate acetylcholinesterase-active sites and turnover in insects - Charpentier_2000_Anal.Biochem_285_76
Author(s) : Charpentier A , Menozzi P , Marcel V , Villatte F , Fournier D
Ref : Analytical Biochemistry , 285 :76 , 2000
Abstract : Acetylcholinesterase is the primary target of organophosphorous and carbamate insecticides. Quantitative changes in acetylcholinesterase are suspected to confer resistance to these insecticides, but a method to estimate the amount in insect is not available. A method using irreversible inhibitors has been developed. Among the irreversible inhibitors tested, 7-(methylethoxyphosphinyloxy)-1-methylquinolinium iodide, chlorpyrifos-ethyl-oxon, and coumaphos-oxon were found to be sufficiently potent and specific.
ESTHER : Charpentier_2000_Anal.Biochem_285_76
PubMedSearch : Charpentier_2000_Anal.Biochem_285_76
PubMedID: 10998265

Title : Exploration of the Drosophila acetylcholinesterase substrate activation site using a reversible inhibitor (Triton X-100) and mutated enzymes - Marcel_2000_J.Biol.Chem_275_11603
Author(s) : Marcel V , Estrada-Mondaca S , Magne F , Stojan J , Klaebe A , Fournier D
Ref : Journal of Biological Chemistry , 275 :11603 , 2000
Abstract : Cholinesterases are activated at low substrate concentration, and this is followed by inhibition as the level of substrate increases. However, one of these two components is sometimes lacking. In Drosophila acetylcholinesterase, the two phases are present, allowing both phenomena to be studied. Several kinetic schemes can explain this complex kinetic behavior. Among them, one model assumes that activation results from the binding of a substrate molecule to a non-productive site affecting the entrance of a substrate molecule into the active site. To test this hypothesis, we looked for an inhibitor competitive for activation and we found Triton X-100. Using organophosphates or carbamates as hemisubstrates, we showed that Triton X-100 inhibits or increases phosphorylation or carbamoylation of the enzyme. In vitro mutagenesis of the residues lining the active site gorge allowed us to locate the Triton X-100 binding site at the rim of the gorge with glutamate 107 playing the major role. These results led to the hypothesis that substrate binding at this site affects the entrance of another substrate molecule into the active site cleft.
ESTHER : Marcel_2000_J.Biol.Chem_275_11603
PubMedSearch : Marcel_2000_J.Biol.Chem_275_11603
PubMedID: 10766776

Title : Effect of tetramethylammonium, choline and edrophonium on insect acetylcholinesterase: test of a kinetic model - Stojan_1999_Chem.Biol.Interact_119-120_137
Author(s) : Stojan J , Marcel V , Fournier D
Ref : Chemico-Biological Interactions , 119-120 :137 , 1999
Abstract : Cholinesterases display a non-Michaelian behaviour with respect to substrate concentration. With the insect enzyme, there is an activation at low substrate concentrations and an inhibition at high concentrations. Previous studies allow us to propose a kinetic model involving a secondary non-productive binding site for the substrate. Unexpectedly, this secondary site has a very high affinity for the substrate when the enzyme is free. On the contrary, when the catalytic site of the enzyme is occupied a strong decrease of this affinity was observed. Moreover, a substrate molecule bound to the peripheral site results in a global decrease of the acylation and/or the deacylation step. Kinetic studies with three reversible inhibitors, tetramethylammonium, edrophonium and choline supported the kinetic model and enable its further refinement.
ESTHER : Stojan_1999_Chem.Biol.Interact_119-120_137
PubMedSearch : Stojan_1999_Chem.Biol.Interact_119-120_137
PubMedID: 10421447

Title : Inhibition of Drosophila acetylcholinesterase by 7-(methylethoxyphosphinyloxy)1-methyl-quinolinium iodide - Stojan_1999_Chem.Biol.Interact_119-120_147
Author(s) : Stojan J , Marcel V , Fournier D
Ref : Chemico-Biological Interactions , 119-120 :147 , 1999
Abstract : The kinetic behaviour of Drosophila melanogaster acetylcholinesterase toward its substrate shows, in comparison with classic Michaelis-Menten kinetics, an apparent homotropic cooperative double activation-inhibition pattern. In order to construct an appropriate kinetic model and obtain further information on the mechanism of the catalytic action of this enzyme, the hydrolysis of acetylthiocholine in the absence and presence of different concentrations of synthetic quaternary methylphosphonate, 7-(methylethoxyphosphinyloxy)1-methyl-quinolinium iodide (MEPQ), was followed on a stopped-flow apparatus. The reaction at low substrate concentrations was followed until the change of the absorbance became negligible and at high concentrations only initial parts were recorded. A simultaneous analysis of the progress curves using numerical integration showed that the powerful organophosphonate inhibitor binds and compete with the substrate for the same binding sites. The results are also in accordance with the hypothesis that virtually every substrate or quasi-substrate molecule that enters into the gorge of active site is hydrolysed.
ESTHER : Stojan_1999_Chem.Biol.Interact_119-120_147
PubMedSearch : Stojan_1999_Chem.Biol.Interact_119-120_147
PubMedID: 10421448

Title : Two invertebrate acetylcholinesterases show activation followed by inhibition with substrate concentration - Marcel_1998_Biochem.J_329_329
Author(s) : Marcel V , Palacios LG , Pertuy C , Masson P , Fournier D
Ref : Biochemical Journal , 329 :329 , 1998
Abstract : In vertebrates there are two cholinesterases, with differences in catalytic behaviour with respect to substrate concentration: butyrylcholinesterase displays an increased activity at low substrate concentrations, whereas acetylcholinesterase displays inhibition by excess substrate. In two invertebrates, Drosophila melanogaster and Caenorhabditis elegans, we found cholinesterases that showed both kinetic complexities: substrate activation at low substrate concentrations followed by inhibition at higher concentrations. These triphasic kinetics can be explained by the presence of two enzymes with different kinetic behaviours or more probably by the existence of a single enzyme regulated by the substrate concentration.
ESTHER : Marcel_1998_Biochem.J_329_329
PubMedSearch : Marcel_1998_Biochem.J_329_329
PubMedID: 9425116

Title : Engineering Sensitive Acetylcholinesterase for Detection of Organophosphate and Carbamate Insecticides -
Author(s) : Villatte F , Marcel V , Estrada-Mondaca S , Fournier D
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. :553 , 1998

Title : Inhibition of acetylcholinesterase by an alkylpyridinium polymer from the marine sponge, reniera sarai - Sepcic_1998_Biochim.Biophys.Acta_1387_217
Author(s) : Sepcic K , Marcel V , Klaebe A , Turk T , Suput D , Fournier D
Ref : Biochimica & Biophysica Acta , 1387 :217 , 1998
Abstract : Large polymeric 3-alkylpyridinium salts have been isolated from the marine sponge Reniera sarai. They are composed of N-butyl(3-butylpyridinium) repeating subunits, polymerized head-to-tail, and exist as a mixture of two main polymers with molecular weights without counterion of about 5520 and 18900. The monomer analogue of the inhibitor, N-butyl-3-butylpyridinium iodide has been synthesized. This molecule shows mixed reversible inhibition of acetylcholinesterase. The polymers also act as acetylcholinesterase inhibitors and show an unusual inhibition pattern. We tentatively describe it as quick initial reversible binding, followed by slow binding or irreversible inhibition of the enzyme. This kinetics suggests that there are several affinity binding sites on the acetylcholinesterase molecule where the polymer can bind. The first binding favors binding to other sites which leads to an apparently irreversibly linked enzyme-inhibitor complex.
ESTHER : Sepcic_1998_Biochim.Biophys.Acta_1387_217
PubMedSearch : Sepcic_1998_Biochim.Biophys.Acta_1387_217
PubMedID: 9748587

Title : A putative kinetic model for substrate metabolisation by Drosophila acetylcholinesterase - Stojan_1998_FEBS.Lett_440_85
Author(s) : Stojan J , Marcel V , Estrada-Mondaca S , Klaebe A , Masson P , Fournier D
Ref : FEBS Letters , 440 :85 , 1998
Abstract : Insect acetylcholinesterase, an enzyme whose catalytic site is located at the bottom of a gorge, can metabolise its substrate in a wide range of concentrations (from 1 microM to 200 mM) since it is activated at low substrate concentrations. It also presents inhibition at high substrate concentrations. Among the various rival kinetic models tested to analyse the kinetic behaviour of the enzyme, the simplest able to explain all the experimental data suggests that there are two sites for substrate molecules on the protein. Binding on the catalytic site located at the bottom of the gorge seems to be irreversible, suggesting that each molecule of substrate which enters the active site gorge is metabolised. Reversible binding at the peripheral site of the free enzyme has high affinity (2 microM), suggesting that this binding increases the probability of the substrate entering the active site gorge. Peripheral site occupation decreases the entrance rate constant of the second substrate molecule to the catalytic site and strongly affects the catalytic activity of the enzyme. On the other hand, catalytic site occupation lowers the affinity of the peripheral site for the substrate (34 mM). These effects between the two sites result both in apparent activation at low substrate concentration and in general inhibition at high substrate concentration.
ESTHER : Stojan_1998_FEBS.Lett_440_85
PubMedSearch : Stojan_1998_FEBS.Lett_440_85
PubMedID: 9862431

Title : Engineering sensitive acetylcholinesterase for detection of organophosphate and carbamate insecticides - Villatte_1998_Biosens.Bioelectron_13_157
Author(s) : Villatte F , Marcel V , Estrada-Mondaca S , Fournier D
Ref : Biosensors & Bioelectronics , 13 :157 , 1998
Abstract : High quantities of various acetylcholinesterases can now be produced following in vitro expression and it is possible to use them as biosensors to detect organophosphates and carbamates insecticides. In order to check the potentialities of acetylcholinesterase from various sources, we have studied enzyme from bovine erythrocyte, Electrophorus electricus, Drosophila melanogaster, Torpedo californica and Caenorhabditis elegans. It appears that insect acetylcholinesterase is more susceptible to a broad range of organophosphates and carbamates insecticides than the other tested enzymes. D. melanogaster is 8-fold more sensitive than E. electricus enzyme and this sensitivity has been increased to 12-fold by introducing a mutation at position 408.
ESTHER : Villatte_1998_Biosens.Bioelectron_13_157
PubMedSearch : Villatte_1998_Biosens.Bioelectron_13_157
PubMedID: 9597732

Title : Variation of dominance of newly arisen adaptive genes - Bourguet_1997_Genetics_147_1225
Author(s) : Bourguet D , Lenormand T , Guillemaud T , Marcel V , Fournier D , Raymond M
Ref : Genetics , 147 :1225 , 1997
Abstract : Newly arisen adaptive alleles such as insecticide resistance genes represent a good opportunity to investigate the theories put forth to explain the molecular basis of dominance and its possible evolution. Dominance levels of insecticide resistance conferred by insensitive alleles of the acetylcholinesterase gene were analyzed in five resistant strains of the mosquito Culex pipiens. Dominance levels were found to differ between strains, varying from partial recessivity to complete dominance. This variation was not explained by differences in catalytic properties of the enzyme, since four of the five resistant strains had identical inhibition properties for the insensitive acetylcholinesterase. Among these four laboratory strains and in individuals collected from natural populations, we found a correlation between increased acetylcholinesterase activities and higher dominance levels. We propose a molecular explanation for how variation in acetylcholinesterase activity may result in variation of dominance level. We also conjecture that the four resistant strains did not differ in their amino acid sequence in the catalytically active regions of acetylcholinesterase, but that the expression of the gene was regulated by either neighboring or distant sites, thereby modifying the dominance level. Under this interpretation, dominance levels may evolve in this system, since heritable variation in acetylcholinesterase activity was found.
ESTHER : Bourguet_1997_Genetics_147_1225
PubMedSearch : Bourguet_1997_Genetics_147_1225
PubMedID: 9383065