Cytochrome oxidase‐catalyzed superoxide generation from hydrogen peroxide

Abstract

Superoxide dismutase is shown to affect spectral changes observed upon cytochroma c oxidase reaction with H₂O₂, which indicates a possibility of O⁻ ₂ radicals being formed in the reaction. Using DMPO as a spin trap, generation of superoxide radicals from H₂O₂ in the presence of cytochrome oxidase is directly demonstrated. The process is inhibited by cyanide and is not observed with a licat-denatured enzyme pointing to a speciric reaction in the oxygen-reducing centre of cytochrome c oxidase. The data support a hypothesis on a catalase cycle catalysed by cylochrome c oxidase in the presence of excess H₂O₂ (Vygodina and Konstantinov (1988) Ann. NY Acad. Sci., 550, 124-138);