Uridine monophosphate synthase (UMPS) (UMPS)

Uridine monophosphate synthase (UMPS) is a bifunctional enzyme that catalyzes the final two steps of the de novo pyrimidine biosynthetic pathway in humans [1, 2]. It possesses two distinct catalytic domains: an N-terminal orotate phosphoribosyltransferase (OPRT), which converts orotate to orotidine 5'-monophosphate (OMP), and a C-terminal orotidine 5'-monophosphate decarboxylase (ODC), which converts OMP to uridine monophosphate (UMP) [3, 12]. This enzyme is essential for the production of pyrimidine nucleotides required for DNA and RNA synthesis, as well as for the formation of metabolic intermediates like UDP-glucose [4, 11]. Genetic deficiency in UMPS results in hereditary orotic aciduria, a rare autosomal recessive disorder characterized by megaloblastic anemia, growth retardation, and excessive urinary excretion of orotic acid [6, 7]. UMPS is a significant target in clinical pharmacology; the OPRT domain is responsible for the metabolic activation of the chemotherapeutic agent 5-fluorouracil (5-FU) into its active, cytotoxic nucleotides [12, 15]. Furthermore, inhibitors of its decarboxylase domain, such as 6-azauridine, have been explored for treating autoimmune diseases and viral infections, highlighting the enzyme's importance as both a therapeutic target and a mediator of drug efficacy [4, 5, 8].

Other names

Uridine 5'-monophosphate synthaseUridine 5'-phosphate synthaseOrotate phosphoribosyltransferase and orotidine-5'-decarboxylaseBifunctional UMP synthaseOPRTase/ODCaseUMPS

The enzyme mediates the de novo synthesis of pyrimidine nucleotides and serves as a critical activator for pyrimidine analog prodrugs like 5-fluorouracil, which are converted by the OPRT domain into cytotoxic metabolites. It is also the site of competitive inhibition by antimetabolites such as 6-azauridine, which specifically block the ODC domain to deplete the cellular supply of UMP.