The aerobic reduction of Fe(III) complexes by hemoglobin and myoglobin.

The ability of hemoglobin (myoglobin) to reduce directly low-molecular-weight complexes of Fe(III) to form methemoglobin (metmyoglobin) and the Fe(II)-tris(2,2'-bipyridine) complex under aerobic conditions is described. The reduction is not mediated by superoxide, O-.2, as shown by increased rates under anaerobic conditions and lack of inhibition by superoxide dismutase. The chemical nature of the Fe(III) complex presented influences the rate of reduction; one of the most effective chelating agents of cellular origin is Fe(III) X ATP. This mechanism may be of fundamental importance in the mobilization and utilization of iron in biological systems.