High Quality Content by WIKIPEDIA articles! Uridine monophosphate synthetase (UMPS) (orotate phosphoribosyl transferase and orotidine-5`-decarboxylase) is the enzyme (EC 4.1.1.23) that catalyses the formation of uridine monophosphate (UMP), an energy-carrying molecule in many important biosynthetic pathways. In humans, the gene that codes for this enzyme is located on the long arm of chromosome 3 (3q13).