superoxiddismutas

Superoxide dismutases (SODs) are metalloenzymes that catalyze the dismutation of the superoxide radical (O2−) into molecular oxygen (O2) and hydrogen peroxide (H2O2). The reaction rapidly reduces the burden of reactive oxygen species and constitutes a core defense against oxidative stress in aerobic organisms. SODs are present in bacteria, archaea, and eukaryotes, and exist in several isoforms with distinct metal cofactors and cellular localizations.

In humans, the best characterized forms are CuZn-SOD (SOD1) in the cytosol and extracellular space, Mn-SOD (SOD2) in mitochondria, and extracellular CuZn-SOD (SOD3). In many microbes, Mn-SODs and Fe-SODs fulfill similar roles. The active sites consist of metal ions that cycle between oxidation states to mediate the dismutation: two superoxide radicals are converted to oxygen and hydrogen peroxide. The produced H2O2 is typically removed by catalase or peroxidases.

Biological and clinical relevance: SODs protect DNA, proteins, and lipids from oxidative damage and influence cellular signaling related to redox status. Mutations in SOD1 are associated with familial amyotrophic lateral sclerosis, illustrating a link between SOD dysfunction and neurodegeneration; altered SOD activity is studied in aging, cancer, and inflammatory diseases. Therapeutic approaches include SOD mimetics and disruption of redox balance, though clinical efficacy varies.

History: SOD activity was first described in 1969 by McCord and Fridovich, establishing a foundational concept in reactive oxygen species biology.