Carbamoyl phosphate synthase II

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Carbamoyl-phosphate synthetase (glutamine-hydrolysing)
EC number6.3.5.5
CAS number37233-48-0
IntEnzIntEnz view
ExPASyNiceZyme view
MetaCycmetabolic pathway
PDB structuresRCSB PDB PDBe PDBsum
carbamoyl-phosphate synthetase 1, aspartate transcarbamylase, and dihydroorotase
Other data
LocusChr. 2 p21

Carbamoyl phosphate synthetase II (EC is an enzyme that catalyzes the reactions that produce carbamoyl phosphate in the cytosol (as opposed to type I, which functions in the mitochondria). Its systemic name is hydrogen-carbonate:L-glutamine amido-ligase (ADP-forming, carbamate-phosphorylating).[1][2][3][4][5][6][7][8]

In pyrimidine biosynthesis, it serves as the rate-limiting enzyme and catalyzes the following reaction:

2 ATP + L-glutamine + HCO3 + H2O 2 ADP + phosphate + L-glutamate + carbamoyl phosphate (overall reaction)
(1a) L-glutamine + H2O L-glutamate + NH3
(1b) 2 ATP + HCO3 + NH3 2 ADP + phosphate + carbamoyl phosphate

It is activated by ATP and PRPP[9] and it is inhibited by UMP (Uridine monophosphate, the end product of the pyrimidine synthesis pathway).

Neither CPSI nor CPSII require biotin as a coenzyme, as seen with most carboxylation reactions.

It is one of the three enzyme functions coded by the CAD gene. It is classified under EC


Carbamoyl-phosphate synthetase (glutamine-hydrolysing) is also known as:

  • hydrogen-carbonate:L-glutamine amido-ligase (ADP-forming, carbamate-phosphorylating)
  • carbamyl phosphate synthetase (glutamine)
  • glutamine-dependent carbamyl phosphate synthetase
  • carbamoyl phosphate synthetase
  • CPS
  • carbon-dioxide:L-glutamine amido-ligase (ADP-forming, carbamate-phosphorylating)


  1. Anderson PM, Meister A (December 1965). "Evidence for an activated form of carbon dioxide in the reaction catalyzed by Escherichia coli carbamyl phosphate synthetase". Biochemistry. 4 (12): 2803–9. doi:10.1021/bi00888a034. PMID 5326356.
  2. Kalman SM, Duffield PH, Brzozowski T (April 1966). "Purification and properties of a bacterial carbamyl phosphate synthetase". The Journal of Biological Chemistry. 241 (8): 1871–7. PMID 5329589.
  3. Yip MC, Knox WE (May 1970). "Glutamine-dependent carbamyl phosphate synthetase. Properties and distribution in normal and neoplastic rat tissues". The Journal of Biological Chemistry. 245 (9): 2199–204. PMID 5442268.
  4. Stapleton MA, Javid-Majd F, Harmon MF, Hanks BA, Grahmann JL, Mullins LS, Raushel FM (November 1996). "Role of conserved residues within the carboxy phosphate domain of carbamoyl phosphate synthetase". Biochemistry. 35 (45): 14352–61. doi:10.1021/bi961183y. PMID 8916922.
  5. Holden HM, Thoden JB, Raushel FM (December 1998). "Carbamoyl phosphate synthetase: a tunnel runs through it". Current Opinion in Structural Biology. 8 (6): 679–85. doi:10.1016/s0959-440x(98)80086-9. PMID 9914247.
  6. Raushel FM, Thoden JB, Reinhart GD, Holden HM (October 1998). "Carbamoyl phosphate synthetase: a crooked path from substrates to products". Current Opinion in Chemical Biology. 2 (5): 624–32. doi:10.1016/s1367-5931(98)80094-x. PMID 9818189.
  7. Raushel FM, Thoden JB, Holden HM (June 1999). "The amidotransferase family of enzymes: molecular machines for the production and delivery of ammonia". Biochemistry. 38 (25): 7891–9. doi:10.1021/bi990871p. PMID 10387030.
  8. Thoden JB, Huang X, Raushel FM, Holden HM (October 2002). "Carbamoyl-phosphate synthetase. Creation of an escape route for ammonia". The Journal of Biological Chemistry. 277 (42): 39722–7. doi:10.1074/jbc.M206915200. PMID 12130656.
  9. Inkling. "Unsupported Browser". Inkling. Retrieved 25 April 2018.

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