Catalyzes the phosphorylation of pyrimidine nucleoside monophosphates at the expense of ATP. Plays an important role in de novo pyrimidine nucleotide biosynthesis. Has preference for UMP and CMP as phosphate acceptors. Also displays broad nucleoside diphosphate kinase activity. ATP + CMP = ADP + CDP ATP + dCMP = ADP + dCDP ATP + UMP = ADP + UDP a 2'-deoxyribonucleoside 5'-diphosphate + ATP = a 2'-deoxyribonucleoside 5'-triphosphate + ADP a ribonucleoside 5'-diphosphate + ATP = a ribonucleoside 5'-triphosphate + ADP Binds 1 Mg(2+) ion per monomer. Monomer. Predominantly cytoplasmic, less than 15% nuclear. Ubiquitously expressed. Consists of three domains, a large central CORE domain and two small peripheral domains, NMPbind and LID, which undergo movements during catalysis. The LID domain closes over the site of phosphoryl transfer upon ATP binding. Assembling and dissambling the active center during each catalytic cycle provides an effective means to prevent ATP hydrolysis. May be produced from an in-frame upstream initiation codon. However, experimental evidence indicates that use of the downstream initiation codon is more likely (isoform 1 sequence). Belongs to the adenylate kinase family. UMP-CMP kinase subfamily. Extended N-terminus.