title: Alpha,beta-unsaturated carbonyl compounds: inhibition of rat liver glutathione S-transferase isozymes and chemical reaction with reduced glutathione.
abstract: Five different alpha,beta-unsaturated carbonyl compounds displayed different reactivities with regard to inhibition of alpha- and mu-class isozymes of rat liver glutathione S-transferases and the chemical reaction with glutathione. Only (E)-2-octenal and (E)-3-nonen-2-one exhibited significant levels of inhibition for each of the rat liver GST isozymes examined. The (E)-2-octenal was more effective as an inhibitor of the alpha-class of isozymes when compared to the mu-class, whereas the (E)-3-nonen-2-one showed a greater degree of inhibition of the mu-class of isozymes relative to the alpha-class. Isozyme 1-1 demonstrated the greatest degree of inhibition with (E)-2-octenal (IC50 = 5.89 microM) of all inhibitor/isozyme combinations. The Ki values for (E)-2-octenal and (E)-3-nonen-2-one toward selected alpha- and mu-class of rat liver glutathione S-transferase isozymes were determined and both of these compounds competitively inhibited all five of the rat liver glutathione S-transferase isozymes examined. The Ki values obtained for these two compounds were significantly different for each of the isozymes except for isozyme 4-4. With the alpha-class of rat liver GST isozymes, (E)-3-nonen-2-one showed a larger Ki value than (E)-2-octenal. Whereas, with the mu-class, (E)-2-octenal exhibited a larger Ki value than (E)-3-nonen-2-one. The rate constants of the forward reaction (k+1), as well as the equilibrium constants (Kd) were determined and the rate constants of the reverse reaction (k-1) were calculated.
authors.affiliation: Department of Toxicology, North Carolina State University, Raleigh 27695.
authors.forename: C I
authors.initials: CI
authors.lastname: Chien
authors.forename: K S
authors.initials: KS
authors.lastname: Kirollos
authors.forename: R J
authors.initials: RJ
authors.lastname: Linderman
authors.forename: W C
authors.initials: WC
authors.lastname: Dauterman
mesh_terms: D000447:Aldehydes / Q000494:pharmacology*; D000475:Alkenes / Q000494:pharmacology*; D000818:Animals; D004952:Esters / Q000494:pharmacology*; D005978:Glutathione / Q000737:chemistry*; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000302:isolation & purification; D007659:Ketones / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008297:Male; D051381:Rats
chemical_list: D000447:Aldehydes; D000475:Alkenes; D004952:Esters; D007527:Isoenzymes; D007659:Ketones; C057348:2-octenal; D005982:Glutathione Transferase; D005978:Glutathione