title: Comparison of the aflatoxin B1-8,9-epoxide conjugating activities of two bacterially expressed alpha class glutathione S-transferase isozymes from mouse and rat.
abstract: The complementary DNAs of rat glutathione S-transferase (GST, EC 2.5.1.18) Yc1 and of mouse Yc were expressed from a prokaryotic expression vector in E. coli. The purified proteins were analyzed for their activity toward aflatoxin B1-8,9-epoxide (AFBO), the reactive intermediate of the fungal mycotoxin aflatoxin B1 (AFB). The mouse Yc isozyme had about 50-fold higher conjugating activity toward AFBO than the rat Yc1 isozyme (144 nmol/mg/min versus 3.3 nmol/mg/min). The rat Yc1 isozyme had specific activities toward 1-chloro-2,4-dinitrobenzene, cumene hydroperoxide and ethacrynic acid of 10.7, 0.98 and 0.92 mumol/mg/min, respectively, whereas the mouse Yc isozyme had specific activities of 5.7, 2.1 and 0.1 mumol/mg/min for these substrates, respectively. These data provide further support for the hypothesis that the constitutive presence of the alpha class GST Yc isozyme in mouse liver protects mice from the hepatocarcinogenic effects of aflatoxin B1.
authors.affiliation: Dept. of Environmental Health, University of Washington, Seattle 98195.
authors.forename: T M
authors.initials: TM
authors.lastname: Buetler
authors.forename: D
authors.initials: D
authors.lastname: Slone
authors.forename: D L
authors.initials: DL
authors.lastname: Eaton
mesh_terms: D016604:Aflatoxin B1 / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D016133:Polymerase Chain Reaction; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping
chemical_list: D007527:Isoenzymes; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; C006426:aflatoxin B1-2,3-oxide; D016604:Aflatoxin B1; D005982:Glutathione Transferase