This protein is a 'fusion' protein encoding four enzymatic activities of the pyrimidine pathway (GATase, CPSase, ATCase and DHOase). 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 (S)-dihydroorotate + H2O = H(+) + N-carbamoyl-L-aspartate Binds 3 Zn(2+) ions per subunit (for dihydroorotase activity). Allosterically regulated and controlled by phosphorylation. 5-phosphoribose 1-diphosphate is an activator while UMP is an inhibitor of the CPSase reaction (By similarity). 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. Pyrimidine metabolism; UMP biosynthesis via de novo pathway; (S)-dihydroorotate from bicarbonate: step 3/3. Homohexamer. Present in the testis but not in the liver. GATase (glutamine amidotransferase) and CPSase (carbamoyl phosphate synthase) form together the glutamine-dependent CPSase (GD-CPSase) (EC 6.3.5.5). In the central section; belongs to the metallo-dependent hydrolases superfamily. DHOase family. CAD subfamily.