This is a tetrameric enzyme with identical subunits, each monomer containing one atom of selenium in the form of a selenocysteine residue. Non-selenium containing glutathione peroxidase enzymes have also been described (Ketterer and Meyer, 1989). Glutathione peroxidase is found both in the cytosol and the mitochondria, and catalyses the removal of hydrogen peroxide from the cell, converting reduced glutathione to oxidized glutathione in the process - thus being one of the key enzymes of the antioxidant system. Glutathione peroxidase can also terminate the chain reaction of lipid peroxidation by removing lipid hydroperoxides from the cell membrane.
Within nervous tissue glutathione peroxidase is localized predominantly in microglia with relatively lower amounts in neurons (Lindenau et al., 1998). When oxidative stress is induced, glutathione peroxidase activity is elevated in microglia and may provide one of the important mechanisms for nervous tissue to withstand oxidative stress.
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