sentences:  Both orotidylate and uridylate are major pyrimidine nucleotides, as uridylate is a precursor to RNA.Uridylate (UMP) is later converted to UDP via phosphorylation by UMP kinase and ATP and then nucleoside diphosphate kinase reversibly phosphorylates UDP to UTP.UTP can then be aminated through catalysis by cytidine triphosphate synthetase to from CTP.