This protein is a 'fusion' protein encoding three enzymatic activities of the pyrimidine pathway (GATase, CPSase, and ATCase). 2 ATP + H2O + hydrogencarbonate + L-glutamine = 2 ADP + carbamoyl phosphate + 2 H(+) + L-glutamate + phosphate carbamoyl phosphate + L-aspartate = H(+) + N-carbamoyl-L-aspartate + phosphate Pyrimidine metabolism; UMP biosynthesis via de novo pathway; (S)-dihydroorotate from bicarbonate: step 1/3. Pyrimidine metabolism; UMP biosynthesis via de novo pathway; (S)-dihydroorotate from bicarbonate: step 2/3. The DHOase domain is defective. GATase (glutamine amidotransferase) and CPSase (carbamoyl phosphate synthase) form together the glutamine-dependent CPSase (GD-CPSase) (EC 6.3.5.5). In eukaryotes EC 6.3.5.5 is synthesized by two pathway-specific (arginine and pyrimidine) genes under separate control. In the central section; belongs to the metallo-dependent hydrolases superfamily. DHOase family. CAD subfamily.