Glutathione-dependent Peroxidase Activities in Rat Submandibular Gland

The activities of Se-dependent glutathione peroxidases and non-Se-dependent glutathione per-oxidase in the submandibular gland were observed using specific substrates. The activities for H₂O₂, cumene hydroperoxide, tert-butyl hydroperoxide, and phosphatidylcholine hydroperoxide were strongly inhibited by iodoacetate. After correction for the activity toward cumene hydroperoxide, it was shown that cumene hydroperoxide is mainly reduced by cytosolic glutathione peroxidase. Although the specific activity was lower than that of cytosolic glutathione peroxidase, phospholipid hydroperoxide glutathione peroxidase showed activity toward not only phosphatidylcholine hydroperoxide but also phosphatidylethanolamine hydroperoxide. These results suggest that cytosolic glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase share a role in the reduction of hydroperoxide, but non-Se-dependent glutathione peroxidase (glutathione S-transferase) plays a lesser role.