NUCLEOTIDE BIOSYNTHESIS
Pyrimidines
Carbamoyl phosphate and aspartate are the pre- cursors of the pyrimidine ring (Figure 14-1). Car- bamoyl phosphate is derived from bicarbonate (the hydrated form of carbon dioxide) and the amido nitrogen of glutamine. An overview of py- rimidine synthesis is shown in Figure 14 Oro- tate 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.