The affinity of mitochondrial oxidative phosphorylation mechanisms for phosphate and adenosine diphosphate.

Abstract

Disruption of [beef heart] mitochondrial membrane structure with digitonin or sonic irradiation leads to greatly decreased affinity of oxidative phosphorylation mechanisms for ADP and for phosphate, as indicated by increased Michaelis constants, without a parallel decline in the P O ratio. Simultaneous-ly, there is a decreased affinity for ADP as an inhibitor 6f ATPase activity and a decreased sensitivity to and affinity for atractyloside, a specific inhibitor of ADP transport. It is proposed that the normally very high affinity of oxidative phosphorylation mechanisms for ADP and phosphate in intact mitochondria is a reflection of the high affinity of specific membrane-linked transport systems for ADP and for phosphate, rather than of the affinity of the.internal phosphorylating enzymes per se.