Manganese superoxide dismutase in rat liver peroxisomes: biochemical and immunochemical evidence

By using highly purified peroxisomes from rat liver, we have shown that peroxisomes contain manganese superoxide dismutase (MnSOD) activity and a 23 kDa protein immunoreactive with antibodies against purified mitochondrial MnSOD. Immunocytochemical studies have also revealed immunoreaction (immunogold) with MnSOD antibodies in mitochondria and peroxisomes. Studies of the intraperoxisomal localization of MnSOD have shown that in peroxisomes MnSOD is a component of the peroxisomal limiting membranes and dense core. Furthermore, the MnSOD level in peroxisomes was modulated by oxidative stress conditions such as ischemia-reperfusion or the treatment with ciprofibrate, a peroxisomal proliferator. These findings suggest that MnSOD in peroxisomes may play an important role in the dismutation of superoxide generated on the peroxisomal membrane for keeping the delicate balance of the redox state.