Meta-Biol

• Pathways

The decarboxylation of orotidine 5'-monophosphate (OMP) to form uridine 5'-monophosphate (UMP) is catalyzed by the orotidine 5'-phosphate decarboxylase activity of the bifunctional "uridine monophosphate synthetase (orotate phosphoribosyl transferase and orotidine 5'-decarboxylase)" protein. While purified human protein has not been characterized in detail, the close similarity of the human gene to that encoding the well-studied hamster protein, and the demonstration that mutations in the human gene are associated with failure to convert orotate to UMP in vivo, provide convincing evidence that the human uridine monophosphate synthetase protein indeed catalyzes these two reactions (McClard et al. 1980; Suchi et al. 1997). The active form of the human protein is a dimer (Yablonski et al. 1996; Wittmann et al. 2008).