Pyrimidine Nucleoside Monophosphokinases
AbstraktA review is a continuation of preceding papers on individual types of nucleoside monophosphokinases (NPM kinases) which catalyze the reversible transfer of the terminal phosphoryl group from a nucleoside triphosphate (in most cases ATP) to nucleoside monophosphates in mammalian tissues. Pyrimidine nucleoside monophosphate kinases (PNP kinases), which catalyse the reversible transfer of gamma-phosphate of ATP to pyrimidine nucleoside monophosphate, have been shown to exist as two distinct enzymes in mammalian cells. One of these enzymes (E.C. 188.8.131.52) acts on dTMP and dCMP. The second enzyme (EC 184.108.40.206) shows a broad substrate specificity, enabling utilization of UMP, dUMP, CMP, and dCMP. The PNP-kinases occupy a strategic position in the biosynthesis of pyrimidine nucleotides since their phosphate acceptor substrates are products of both the de novo and the salvage pathways. We report on the recent knowledge of general properties, mechanism, and three- dimensional structure of dTMP-kinases from different sources; their similarity to AMP- and GMP-kinases, respectively, is also discussed.