The effect of mitochondrial energization on cytochrome c oxidase kinetics as measured at low temperatures. II. The binding and reduction of dioxygen.

The effect of pre-energization of isolated mitochondria by ATP at room temperature upon the kinetics of oxygen intermediates (measured at very low temperatures) of cytochrome c oxidase has been studied. It was found that "energization" of mitochondria at room temperature had dramatic effects on several partial reactions of cytochrome aa3. Thus, in the "energized" frozen state, the rate of O2 binding to ferrous cytochrome a3 and the subsequent formation of the "peroxy" compound B are accelerated, while oxidation of cytochromes c and c1 is inhibited. These effects of ATP are abolished by oligomycin and uncoupling agents and may, therefore, be reflections of the coupling of the mitochondrial ATP synthetase to the respiratory chain at the level of cytochrome c oxidase, which is the basis of the mechanism of coupling respiration to ATP synthesis and respiratory control.