OXIDATIVE MODIFICATION AND INACTIVATION OF SUPEROXIDE-DISMUTASE BY HYPOCHLORITE

Hypochlorite-induced oxidative inactivation of Cu,Zn-superoxide dismutase (SOD) from bovine erythrocytes was studied. Sodium dodecyl sulfate gel electrophoresis and isoelectric focusing showed that the oxidation induces degradation of the polypeptide chain, formation of aggregates, and the appearance of isoforms. These modified Protein forms differ from native SOD in electric charge and molecular weight, but still possess catalytic activity. The modified forms of SOD appear to result from intramolecular cross-linking of amino and aldehyde groups, as indicated by the appearance of a long wavelength fluorescence maxima characteristic of such links. The inactivation of SOD is assumed to be due to the oxidation of amino acids located outside the active site of the enzyme,