Human erythrocyte pyrimidine nucleoside monophosphate kinase. Partial purification and properties of two allelic gene products.

Human pyrimidine nucleoside monophosphate kinase is a polymorphic enzyme having two allelic gene products, UMPK 1 and UMPK 2, in several populations. A procedure is described for the partial purification of this enzyme from human red blood cells resulting in a 1500-fold purification of the enzyme for UMPK 1 and 583-fold for UMPK 2. The purified enzyme preparation catalyzed the phosphorylation of UMP, CMP, and dCMP, and used ATP as the preferred phosphate donor. The heavy metals, mercury, and copper, were found to be strong inhibitors of pyrimidine nucleoside monophosphate kinase activity. EDTA was found to protect the enzyme from inactivation by the heavy metals, and 2-mercaptoethanol stabilized the enzyme during purification. UMPK 1 and UMPK 2 were found to have similar kinetic properties; however, UMPK 2 had a slower electrophoretic mobility and greater thermolability than UMPK 1.