General Superoxide dismutase

ribbon diagram of bovine cu-zn sod subunit








copper , zinc – commonly used eukaryotes, including humans. cytosols of virtually eukaryotic cells contain sod enzyme copper , zinc (cu-zn-sod). example, cu-zn-sod available commercially purified bovine red blood cells. bovine cu-zn enzyme homodimer of molecular weight 32,500. first sod atomic-detail crystal structure solved, in 1975. 8-stranded greek key beta-barrel, active site held between barrel , 2 surface loops. 2 subunits tightly joined back-to-back, hydrophobic , electrostatic interactions. ligands of copper , zinc 6 histidine , 1 aspartate side-chains; 1 histidine bound between 2 metals.
iron or manganese – used prokaryotes , protists, , in mitochondria , chloroplasts

iron – many bacteria contain form of enzyme iron (fe-sod); bacteria contain fe-sod, others mn-sod, , (such e. coli) contain both. fe-sod can found in chloroplasts of plants. 3d structures of homologous mn , fe superoxide dismutases have same arrangement of alpha-helices, , active sites contain same type , arrangement of amino acid side-chains. dimers, tetramers.
manganese – mitochondria, , many bacteria, contain form manganese (mn-sod): example, mn-sod found in human mitochondria. ligands of manganese ions 3 histidine side-chains, aspartate side-chain , water molecule or hydroxy ligand, depending on mn oxidation state (respectively ii , iii).


nickel – prokaryotic. has hexameric (6-copy) structure built right-handed 4-helix bundles, each containing n-terminal hooks chelate ni ion. ni-hook contains motif his-cys-x-x-pro-cys-gly-x-tyr; provides of interactions critical metal binding , catalysis , is, therefore, diagnostic of nisods.

in higher plants, sod isozymes have been localized in different cell compartments. mn-sod present in mitochondria , peroxisomes. fe-sod has been found in chloroplasts has been detected in peroxisomes, , cuzn-sod has been localized in cytosol, chloroplasts, peroxisomes, , apoplast.