Enzymatic Synthesis of Triphosphopyridine Nucleotide

Von Euler and Vestin (1) demonstrated the synthesis of triphosphopyridine nucleotide (TPN) when diphosphopyridine nucleotide (DPN) was incubated with adenosine triphosphate (ATP) in the presence of crude yeast maceration juice. In subsequent reports (2) from the Stockholm laboratory, several mechanisms for this reaction were considered but none was established. With crude pigeon liver fractions, Mehler et al. (3) observed the formation of TPN when DPN and ATP were incubated together; no synthesis was observed in the absence of either DPN or ATP. While the findings with the yeast and liver preparations were compatible with a direct phosphorylation of DPN by ATP, it was difficult to reconcile the observations of Altman and Evans (4) with this mechanism. These investigators found that TPN synthesis by an aqueous extract of pigeon liver acetone powder took place without added DPN. Also, adenylic acid replaced ATP, and nicotinamide originally present in the aqueous extract was completely converted to TPN. Most recently, studies on the enzymatic synthesis of DPN and flavin-adenine dinucleotide (FAD) have suggested another possible mechanism (5, 6). The demonstrated condensation of nicotinamide mononucleotide (NMN) and flavin mononucleotide with ATP to form DPN and FAD, respectively, made it desirable to ascertain whether an analogous mechanism obtained for TPN synthesis. An enzyme has now been partially purified from autolysates of ale yeast which catalyzes the synthesis of TPN by a direct phosphorylation of DPN by ATP: