Inorganic orthophosphate activation and adenosine diphosphate as the primary phosphoryl acceptor in oxidative phosphorylation.

Experiments are reported showing that in net oxidative phosphorylation by submitochondrial particles ADP furnishes the terminal bridge oxygen in the ATP formed. In contrast to ADP, AMP does not suffice to activate a inorganic orthophosphate -F? HOH exchange by submitochondrial particles. In sensitive initial labeling experiments during net oxidative phosphorylation, “Pi appears initially in ATP, not in ADP. The results show that ADP is the first demonstrable nucleotide acceptor for a phosphoryl group in oxidative phosphorylation and that an oxygen from Pi forms water.