Rat hepatic cytosolic glutathione-dependent enzyme protection against lipid peroxidation in the NADPH-microsomal lipid peroxidation system.

ABSTRACT

Dialyzed rat liver cytosol (105 000 X g supernatant), when added along with 2.5 mM glutathione, blocked malonaldehyde formation in the NADPH-microsomal lipid peroxidation system, thus protecting against lipid peroxidation. Preheating the cytosol for 10 min at 60 degrees C destroyed its protective ability. Ammonium sulfate fractionation and Sephadex G-100 gel filtration of cytosol indicated that more than one glutathione-dependent protective enzyme was present. Fractions from the G-100 column containing the selenoenzyme glutathione peroxidase failed to protect, but fractions containing the glutathione S-transferases, which have non selenium-dependent glutathione peroxidase activity, did protect. The glutathione S-transferases were purified further with ion exchange chromatography and shown to have protective activity. Thus the rat hepatic cytosolic glutathione-dependent enzyme protection against lipid peroxidation in the NADPH-microsomal lipid peroxidation system is in part due to some of the glutathione S-transferases. The selenium-dependent glutathione peroxidase appears to have no protective effect in this system.