A manganese-containing superoxide dismutase from Paracoccus denitrificans.

A cyanide-insensitive superoxide dismutase (superoxide: superoxide dismutase EC 1.15.1.1) has been isolated from Paracoccus denitrificans, purified to homogeneity and characterized. It is a soluble, manganese-containing protein with an apparent molecular weight of 41 500 +/- 1000. It is composed of two identical subunits (Mr 23 500) not bound by disulfide linkage. It's isoelectric point is 4.5. The amino acid composition shows strong similarities with other dimeric procaryotic and with tetrameric mitochondrial Mn-superoxide dismutases. The fully active enzyme contained from 1.34 to 2 gatom Mn/mol enzyme.