Carbamoyl phosphate and aspartate are the pre- cursors of the pyrimidine ring (Figure 14-1).
Carbamoyl phosphate is derived from bicarbonate (the hydrated form of carbon dioxide) and the amido nitrogen of glutamine.
An overview of pyrimidine synthesis is shown in Figure 14 Orotate is the first pyrimidine formed in the pathway, and orotidine 5'-monophosphate (OMP) is the first pyrimidine nucleotide.
The nucleotides of uracil, cytosine, and thymine are derived from OMP, which occupies a central position in pyrimidine formation.