Superoxide dismutases enhance the rate of autoxidation of 3-hydroxyanthranilic acid

The autoxidation of 3-hydroxyanthranilate to cinnabarinate at 37 degrees C and at pH 7.4 is hastened by superoxide dismutase (SOD). The Cu,Zn-containing enzyme from bovine erythrocytes and the Mn-containing enzyme from Escherichia coli were equally effective in this regard; whereas the H2O2-inactivated Cu,Zn enzyme was ineffective. Catalase appears to augment the effect of superoxide dismutase, because it prevents the bleaching of cinnabarinate by H2O2. It follows that O2-, which is a product of the autoxidation, slows the net autoxidation by engaging in back reactions and that SOD increases the rate of autoxidation by removal of O2- and thus by prevention of these back reactions.