superoxiddismutaser

Superoxiddismutaser, commonly called superoxide dismutase (SOD), is an essential metalloenzyme that catalyzes the conversion of superoxide radicals (O2−) into molecular oxygen and hydrogen peroxide. This reaction reduces oxidative stress by removing a reactive oxygen species produced during respiration and inflammation. In humans and many other organisms, SOD exists in several forms that differ in location, metal cofactor, and amino acid sequence.

The three major human isoforms are SOD1 (Cu/Zn-SOD) in the cytosol and in the intermembrane space, SOD2 (Mn-SOD) in mitochondria, and SOD3 (Cu/Zn-SOD) that is secreted into extracellular spaces. SOD1 is a homodimer with a copper and a zinc ion in the active site; SOD2 is a manganese-containing homotetramer; SOD3 is secreted and also Cu/Zn-containing. In bacteria and some archaea, additional forms exist, such as Fe-SOD and Ni-SOD.

The generic reaction is: 2 O2− + 2 H+ → O2 + H2O2. The hydrogen peroxide is further detoxified by catalase, glutathione peroxidase, or peroxiredoxins. Maturation and activity depend on metal incorporation by chaperone proteins (e.g., CCS for SOD1) and proper disulfide formation in SOD1.

Dysfunction or reduced activity of SOD, especially SOD1 mutations, is linked to neurodegenerative diseases including familial amyotrophic lateral sclerosis. SOD activity serves as a biomarker in some pathologies and is studied in aging and inflammatory contexts.

Discovery of SOD is attributed to McCord and Fridovich, who first described and characterized the enzyme in 1969.