Figure 2.
De novo pyrimidine biosynthesis pathway. Carbamoyl Phosphate Synthetase II (CPS2), the cytosolic form of the enzyme CPS1 found in the mitochondrial matrix taking part in the urea cycle, catalyses the reaction leading to the formation of carbamoyl phosphate from HCO3−, glutamine, ATP and water. The generated carbamoyl phosphate and aspartate are used to generate pyrimidines though the steps as seen above. Note that thymidine 5ʹ-triphosphate (TTP), another pyrimidine is generated from CTP. Those marked * are components of the CAD complex.8,25,26