Orotidine 5'-monophosphate (OMP), also known as orotidylic acid, is a pyrimidine nucleotide[1] which is the last intermediate in the biosynthesis of uridine monophosphate.[2] OMP is formed from orotate and phosphoribosyl pyrophosphate by the enzyme orotate phosphoribosyltransferase.
In humans, the enzyme UMP synthase converts OMP into uridine 5'- monophosphate. If UMP synthase is defective, orotic aciduria can result.