Catalyzes the reversible phosphorylation of UMP to UDP, with ATP as the most efficient phosphate donor. Is also able to phosphorylate dUMP. ATP + UMP = ADP + UDP Unlike other bacteria, is not activated by GTP. UTP is a competitive inhibitor against UMP and a non-competitive inhibitor toward ATP. Positive cooperativity is observed with ATP as variable substrate, but it is abolished in the presence of UTP. Optimum pH is 6.8. Pyrimidine metabolism; CTP biosynthesis via de novo pathway; UDP from UMP (UMPK route): step 1/1. Homohexamer; trimer of dimers. Belongs to the UMP kinase family.