DEMONSTRATION OF GLUTATHIONE-PEROXIDASE IN RAT-LIVER PEROXISOMES AND ITS INTRAORGANELLAR DISTRIBUTION

Earlier, we reported that rat liver peroxisomes contain Cu-Zn superoxi de dismutase (J. Biol. Chem. 267, 6870), thereby suggesting a new anti oxidant role for this organelle in free radical metabolism. In this st udy, we report for the first time that mammalian peroxisomes also cont ain glutathione peroxidase. Using highly purified rat Liver peroxisome s isolated by Nycodenz gradient, we found that peroxisomes contain glu tathione peroxidase which shows enzymatic activity with different subs trates such as hydrogen peroxide, cumene hydroperoxide, and t-butyl hy droperoxide. This activity could be inhibited in vitro by mercaptosucc inate. Western blot analysis revealed that peroxisomes from control an d ciprofibrate-treated Livers show immunoreactive bands with antibodie s raised against glutathione peroxidase. The intraperoxisomal distribu tion of glutathione peroxidase was investigated by using peroxisomal m embrane and matrix proteins. The results revealed that glutathione per oxidase is a matrix enzyme. The presence of glutathione peroxidase in peroxisomes provides an alternate enzyme system responsible for the de gradation of organic peroxides and the degradation of H2O2 under condi tions in which catalase is inactivated (e.g., ischemia-reperfusion and endotoxemia). These findings suggest that glutathione peroxidase in p eroxisomes may play a novel role in the cellular antioxidant responses to various oxidative stress conditions. (C) 1994 Academic Press, Inc.