We report here that the trifunctional carbamoyl-phosphate synthase, aspartate transcarbamoylase, and dihydroorotase (CAD) activates the pentose phosphate pathway (PPP) and serine synthesis pathway (SSP) to promote de novo nucleotide synthesis via deamidation. Biochemical analyses show that CAD interacts with and deamidates glucose-6-phosphate dehydrogenase (G6PD) and phosphoglycerate dehydrogenase (PHGDH), which are rate-limiting enzymes of the PPP and SSP, respectively.