Spectral Intermediate in the Reaction of Ferrous Cytochrome P450 cam with Superoxide Anion

Abstract

The addition of KO 2 to ferrous cytochrome P450 cam 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 P450 cam reacts with O − 2 to form an intermediate species of the enzyme, of which spectrum is closely similar to that of the oxygenated form of P450 cam. Subsequently, the intermediate was converted to native ferric P450 cam. In contrast, ferrous form of horseradish peroxidase reacted with O − 2 to form Compound I of the enzyme without detection of intermediates.