Purification and some properties of glutathione-S-epoxide transferase from guinea pig liver

Glutathione-S-epoxide transferase has been purified from guinea pig liver in a homogeneous form having a sedimentation coefficient, s20,w of 3.8S, and a molecular weight of 46,000, and dissociable into subunits with a molecular weight of 25,000. The activities with four substrates, styrene oxide, naphthalene oxide, iodomethane, and p-nitrobenzyl chloride, were all copurified during purification of the enzyme from 100,000 X g supernatant of guinea pig liver. However, kinetic data suggest different mechanisms for the glutathione conjugating reaction with iodomethane and p-nitrobenzyl chloride. The view that the epoxide transferase does not distinguish between simple epoxides and arene oxides has been confirmed with the guinea pig liver enzyme.