Does oxidative phosphorylation increase the rate of creatine phosphate synthesis in heart mitochondria or not?

Abstract

The rates of creatine phosphate synthesis in the mitochondrial creatine phosphokinase reaction under different conditions have been re-examined. It has been shown that in actively respiring mitochondria creatine phosphate synthesis from matrix ATP occurs with a rate close to the maximal rate of the forward creatine phosphokinase reaction. When oxidative phosphorylation was inhibited but ATP was kept constant by the regenerating system, the rate of creatine phosphate synthesis was significantly lower and corresponded to that predicted on the basis of the kinetic equation for creatine phosphokinase. The sources of discrepancies between these data and the results recently reported by Altschuld and Brierley [ Journal of Molecular and Cellular Cardiology (1977), 2, 875–896] have been considered. It is concluded that the low rates of creatine phosphate synthesis reported by these authors are related to very low respiratory activity observed in their experiments and unfavorable reaction mixture composition. Intracellular distribution of creatine phosphokinase in heart muscle has also been briefly considered.