Enzymatic synthesis of nucleoside diphosphates and triphosphates.

It has been recognized from recent studies that nucleoside triphosphates, other than ATP,’ function in biologic systems as phosphorylating agents (1) and in coenzyme synthesis (2) in a manner analogous to that of ATP. The discovery of the natural occurrence of a variety of purine and pyrimidine nucleoside diand triphosphates (3-5) and the likelihood that new biologic functions for these nucleotides will be found increased our interest in the mechanism of their biosynthesis. Several pathways are known for the formation of UTP, including its origin from UDP, by the action of pyruvate’ phosphokinase (6) or of nucleoside diphosphate kinase (7), but no mechanism has been elucidated for the synthesis of UDP or UTP from U5P. In a preliminary communication (8), we have reported that extracts of yeast and liver which convert erotic acid to U5P also bring about the synthesis of UDP and UTP. A subsequent report (9) described the action of a partially purified enzyme preparation from yeast which effects a transphosphorylation between adenosine, uridine, and guanosine nucleotides (equations (1) to (5)) and differs from muscle myokinase (10, 11) which acts on adenosine nucleotides only.