Abstract: The present invention provides the cDNA for a novel nucleoside/nucleotide monophosphate kinase cloned from a human macrophage cDNA library. This kinase is able to phosphorylate UMP and utilize multiple phosphate donors, but has demonstrated a preference for transferring a phosphate from ATP or UTP to cytidine monophosphate (CTP). The kinase is thus referred to as cytidine monophosphate (CMP) kinase. This kinase is shown to be a Mg2+ dependent nucleotide kinase which codes for two ubiquitously transcribed mRNA splice products of 3.2 and 2.0 kb, and has been mapped to chromosome 1, region p32-34.1, a region known to contain other nucleotide modifying enzyme genes.