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, but can also use AMP and dCMP to a lesser extent. May play a role during the formation of basidiospores in the gill tissue. ATP + UMP = ADP + UDP Binds 1 Mg(2+) ion per monomer. Monomer. Predominantly cytoplasmic. 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 GTP binding. Assembling and disassembling the active center during each catalytic cycle provides an effective means to prevent GTP hydrolysis (By similarity). Belongs to the adenylate kinase family. UMP-CMP kinase subfamily.