Guanylate kinase has been identified and partially purified from human erythrocytes. A simple method has been developed, using calcium phosphate gel and DEAE-cellulose, for the purification of guanylate kinase and several other erythrocytic enzymes such as purine nucleoside phosphorylase, nucleoside diphosphokinase, adenylate kinase, lactic dehydrogenase, pyruvate kinase and phosphoglucose isomerase. The method is adaptable for both small and large scale purification and has been applied successfully to as much as 40 to 50 1. of human blood. Studies with the partially purified erythrocytic guanylate kinase showed that GMP, dGMP, 8-azaGMP and IMP serve as substrates while UMP, CMP and 6-thioIMP do not. 6-ThioGMP was not a substrate but was a competitive inhibitor with GMP with a K1 of 7·5 × 10-5 M. Preliminary findings suggest the occurrence of several isozymes of this enzyme. Other kinetic parameters of the enzyme are described.
ASJC Scopus subject areas