Glutathione peroxidase isolated from plasma reduces phospholipid hydroperoxides

The reactivities of a selenoenzyme, glutathione peroxidase isolated from plasma, against phosphatidylcholine hydroperoxides and photoperoxidized erythrocyte ghosts have been investigated. Glutathione peroxidase isolated from plasma was found to catalyze the reduction of phosphatidylcholine hydroperoxides to the corresponding hydroxy derivatives. The enzyme is also capable of reducing the hydroperoxides in photoperoxidized ghosts. Thin layer chromatographic analysis of enzyme-treated ghosts revealed that plasma glutathione peroxidase can reduce phospholipid-derived hydroperoxides but cannot reduce cholesterol hydroperoxides. These studies demonstrate that the three known glutathione peroxidase (cellular, plasma, and phospholipid hydroperoxide) differ from each other in substrate specificity.