The components of choline oxidase and aerobic phosphorylation coupled with choline oxidation.

It is now generally agreed that in the process of aerobic oxidative phosphorylations there is no direct interaction of orthophosphate with the various oxidizable substrates which provide the energy necessary for the phosphorylation. Phosphorylation takes place during the passage of electrons from substrate to molecular oxygen. Since there are three main oxidationreduction systems of varied potentials distributed in this pathway (pyridine nucleotides, flavoproteins, and the cytochrome-cytochrome osidase system), it was logical to assume that the energy necessary for phosphorylation was provided by these oxidation-reduction reactions. Lehninger (1) offered the first conclusive demonstration of the coupling of phosphorylation with the oxidation of dihydrodiphosphopyridine nucleotide (DPNH) by oxygen, in which adenosinediphosphate was phosphorylated to adenosinetriphosphate (ATP) with a P: DPNH ratio of about 1.5. Hummel and Lindberg (2) and Good and Leaf (3) have reported phosphorylation of flavin-adenine dinucleotide, although the exact relationship of this finding to oxidative phosphorylations is not clear. Some unsuccessful attempts have been made to link phosphorylations to electron transport with the third group of oxidation-reduction systems, the cytochrome-cytochrome oxidase system (4, 5). Phosphorylation at the substrate level seems to be confined to the obligatory anaerobic phase of carbohydrate fermentation, and to acyl coenzyme A phosphorylations, in which, in the presence of the phosphorylating enzyme, the energy of the thio ester bond of acyl coenzyme A is utilized to generate the energy-rich phosphate bond of adenosinetriphosphate (6, 7). Phosphorylations were thought at first to be limited to reactions of carbohydrate fermentation and oxidation. Lehninger’s dis-