Identification of a Phosphate-incorporating Protein from Bovine Liver as Nucleoside Diphosphate Kinase and Isolation of l-32P-Phosphohistidine, 3-32P-Phosphohistidine, and N-ε-32-P-Phospholysine from Erythrocytic Nucleoside Diphosphate Kinase, Incubated with Adenosine Triphosphate-32P

A purified bovine liver protein, which was recently shown to be rapidly phosphorylated on incubation with AT32P, has been identified as a nucleoside diphosphate kinase (EC 2.7.4.6). Human erythrocytic nucleoside diphosphate kinase was therefore incubated with AT32P and degraded by alkaline hydrolysis, in order to compare the phosphorylated degradation products with those from liver nucleoside diphosphate kinase incubated with AT32P. In accordance with previous results with the liver enzyme, 1-32P-phosphohistidine, 3-32P-phosphohistidine, and N-e-32P-phospholysine could all be isolated from AT32P-incubated erythrocytic nucleoside diphosphate kinase. The additional radioactive products obtained from the two 32P-labeled nucleoside diphosphate kinases were found to be identical, as judged by paper electrophoresis, indicating active sites of the same or similar structure.