Plasma glutathione peroxidase reduces phosphatidylcholine hydroperoxide

The reducing activity of rat plasma glutathione peroxidase on phosphatidylcholine hydroperoxide (PC-OOH) and cholesteryl ester hydroperoxide (CE-OOH) was examined since these hydroperoxides are the major oxidation products of plasma. PC-OOH was reduced by the enzyme while CE-OOH was not. The reduction of PC-OOH by the enzyme ceased when all thiol was consumed, but the activity was recovered by the addition of glutathione, suggesting glutathione is important to keep the enzyme in the reduced form. These results are consistent with the findings that CE-OOH is present in human and rat plasmas while PC-OOH is undetectable and suggest that one of the physiological roles of the enzyme is to reduce PC-OOH.