Aerobic Reduction of Cytochrome b566 in I (succinate-cytochrome cl reductase/stopped-flow kinetics

In anaerobic, uncoupled pigeon-heart mitochondria treated with oxidizable substrate, the cyto- chrome b566 remains largely oxidized. In the presence of antimycin A, addition of oxygen induces a reduction of this cytochrome. The rate of cytochrome b566 reduction is comparable to and dependent on the rate of cytochrome ci oxidation. Kinetic data suggest that either ubiquinone or another donor of similar potential provides electrons for the reduction of cytochrome b566. It is postulated that the aerobic reduction of cytochrome b566 is directly related to the energy conservation at site II.