Spectral intermediate in the reaction of ferrous cytochrome P450cam with superoxide anion

The addition of KO2 to ferrous cytochrome P450cam in the presence of d-camphor under anaerobic condition resulted in the formation of exo- and endo-5-hydroxycamphor. The product formation was inhibited by the addition of superoxide dismutase, not catalase. The ferrous form of P450cam reacts with O2- to form an intermediate species of the enzyme, of which spectrum is closely similar to that of the oxygenated form of P450cam. Subsequently, the intermediate was converted to native ferric P450cam. In contrast, ferrous form of horseradish peroxidase reacted with O2- to form Compound I of the enzyme without detection of intermediates.