Reduction of cytochrome c by hydrogen peroxide and its inhibition by superoxide dismutase.

Ferricytochrome c is slowly converted by hydrogen peroxide to an equilibrium mixture of ferricytochrome c and ferrocytochrome c, and in the process, the hydrogen peroxide is decomposed. The reductant appears to be superoxide anion, produced from the reaction of hydrogen peroxide with oxygen. Because the reduction of ferricytochrome c by hydrogen peroxide is inhibited by superoxide dismutase, we propose that the enzyme acts by converting superoxide anion to a dimerized product that is less active as a reductant.