– Superoxide dismutases (SOD) are important anti-oxidant enzymes that guard against superoxide toxicity. In humans, as in all mammals and most chordates, three forms of superoxide dismutase (SOD) are present: SOD1 is located in the cytoplasm, SOD2 in the mitochondria, and SOD3 is extracellular. Mitochondrial superoxide dismutase [SOD; manganese SOD (MnSOD) or SOD2] neutralizes highly reactive superoxide radical (O•-2), the first member in the plethora of mitochondrial reactive oxygen species.