Tamura H

References (3)

Title : Loop of Streptomyces Feruloyl Esterase Plays an Important Role in the Enzyme's Catalyzing the Release of Ferulic Acid from Biomass - Uraji_2018_Appl.Environ.Microbiol_84_
Author(s) : Uraji M , Tamura H , Mizohata E , Arima J , Wan K , Ogawa K , Inoue T , Hatanaka T
Ref : Applied Environmental Microbiology , 84 : , 2018
Abstract : Feruloyl esterases (FAEs) are key enzymes required for the production of ferulic acid from agricultural biomass. Previously, we identified and characterized R18, an FAE from Streptomyces cinnamoneus NBRC 12852, which showed no sequence similarity to the known FAEs. To determine the region involved in its catalytic activity, we constructed chimeric enzymes using R18 and its homolog (TH2-18) from S. cinnamoneus strain TH-2. Although R18 and TH2-18 showed 74% identity in their primary sequences, the recombinant proteins of these two FAEs (recombinant R18 [rR18] and rTH2-18) showed very different specific activities toward ethyl ferulate. By comparing the catalytic activities of the chimeras, a domain comprised of residues 140 to 154 was found to be crucial for the catalytic activity of R18. Furthermore, we analyzed the crystal structure of rR18 at a resolution of 1.5 A to elucidate the relationship between its activity and its structure. rR18 possessed a typical catalytic triad, consisting of Ser-191, Asp-214, and His-268, which was characteristic of the serine esterase family. By structural analysis, the above-described domain was found to be present in a loop-like structure (the R18 loop), which possessed a disulfide bond conserved in the genus Streptomyces Moreover, compared to rTH2-18 of its parental strain, the TH2-18 mutant, in which Pro and Gly residues were inserted into the domain responsible for forming the R18 loop, showed markedly high kcat values using artificial substrates. We also showed that the FAE activity of TH2-18 toward corn bran, a natural substrate, was improved by the insertion of the Gly and Pro residues.IMPORTANCEStreptomyces species are widely distributed bacteria that are predominantly present in soil and function as decomposers in natural environments. They produce various enzymes, such as carbohydrate hydrolases, esterases, and peptidases, which decompose agricultural biomass. In this study, based on the genetic information on two Streptomyces cinnamoneus strains, we identified novel feruloyl esterases (FAEs) capable of producing ferulic acid from biomass. These two FAEs shared high similarity in their amino acid sequences but did not resemblance any known FAEs. By comparing chimeric proteins and performing crystal structure analysis, we confirmed that a flexible loop was important for the catalytic activity of Streptomyces FAEs. Furthermore, we determined that the catalytic activity of one FAE was improved drastically by inserting only 2 amino acids into its loop-forming domain. Thus, differences in the amino acid sequence of the loop resulted in different catalytic activities. In conclusion, our findings provide a foundation for the development of novel enzymes for industrial use.
ESTHER : Uraji_2018_Appl.Environ.Microbiol_84_
PubMedSearch : Uraji_2018_Appl.Environ.Microbiol_84_
PubMedID: 29150515
Gene_locus related to this paper: strcj-estA

Title : Endocrine disruptors that disrupt the transcription mediated by androgen receptor - Tamura_2008_J.Pestic.Sci_33_33
Author(s) : Tamura H , Hosoda A , Akamatsu M
Ref : Journal of Pesticide Science , 33 :33 , 2008
Abstract : The Ministry of Environment in Japan (formerly the Japan Environment Agency) has made a priority list of compounds, SPEED 98, to preferentially examine whether they act as endocrine active chemicals and conducted a project to scientifically address endocrine disruptor issues. Out of around 100 compounds listed in SPEED 98 and related compounds, thirty-six acted as pure androgen receptor (AR) antagonists, whereas 13 showed both AR agonist and antagonist activities based on an in vitro reporter gene assay. The structural difference between AR agonists and antagonists was explained by Comparative Molecular Field Analysis (CoMFA). The precise structural requirements for AR agonists and/or antagonists are described as follows: in the case of AR agonist, the distance between two functional groups with H-bonding ability corresponding to 3-keto and 17beta-OH groups should be near 10 A to maintain a favorable H-bond position while the length axis of antagonists should be less than or more than 10 A so as not to make an H-bond by interaction with Asn705 and Thr877 in the steroid D ring anchoring pocket, preventing the correct positioning of helix 3 (H3) and helix 12 (H12). This hypothetical general rule is named .
ESTHER : Tamura_2008_J.Pestic.Sci_33_33
PubMedSearch : Tamura_2008_J.Pestic.Sci_33_33

Title : Androgen receptor antagonism by the organophosphate insecticide fenitrothion - Tamura_2001_Toxicol.Sci_60_56
Author(s) : Tamura H , Maness SC , Reischmann K , Dorman DC , Gray LE , Gaido KW
Ref : Toxicol Sci , 60 :56 , 2001
Abstract : Organophosphate insecticides represent one of the most widely used classes of pesticides with high potential for human exposure in both rural and residential environments. We investigated the interaction of the organophosphothioate pesticide fenitrothion (O,O-dimethyl O-(4-nitro-m-tolyl) phosphorothioate) with the human androgen receptor (AR). Fenitrothion blocked dihydrotestosterone-dependent AR activity in a concentration-dependent and competitive manner in HepG2 human hepatoma liver cells transiently transfected with human AR and an AR-dependent luciferase reporter gene. Schild regression analysis yielded an equilibrium dissociation constant value of 2.18 x 10(-8) M. To determine the antiandrogenic potential of fenitrothion in vivo, 7-week-old castrated Sprague-Dawley rats were dosed once a day for 7 days with testosterone propionate (50 microg/day, sc) plus gavage doses of either corn oil vehicle or fenitrothion (15 or 30 mg/kg/day). An additional group of rats was given testosterone propionate and flutamide (50 mg/kg/day). Motor activity and acetylcholinesterase activity in whole blood and brain were also assessed. Both fenitrothion and the reference antiandrogen flutamide caused significant decreases in the ventral prostate, seminal vesicle, and levator ani plus bulbocavernosus muscles tissue weights. In contrast, blood acetylcholinesterase activity, a standard biomarker of organophosphate poisoning, was only inhibited at the higher dose of fenitrothion (30 mg/kg). Our results demonstrate that fenitrothion is a competitive AR antagonist, comparable in potency to the pharmaceutical antiandrogen flutamide and more potent, based on in vitro assays, than the known environmental antiandrogens linuron and p,p'-, 2,2-bis(p-hydroxyphenyl)-1,1-dichloroethylene ( p,p'-DDE).
ESTHER : Tamura_2001_Toxicol.Sci_60_56
PubMedSearch : Tamura_2001_Toxicol.Sci_60_56
PubMedID: 11222873