ExplorEnz: EC 6.3.5.5

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6.3.5.5

Accepted name:

carbamoyl-phosphate synthase (glutamine-hydrolysing)

Reaction:

2 ATP + L-glutamine + hydrogencarbonate + H₂O = 2 ADP + phosphate + L-glutamate + carbamoyl phosphate (overall reaction)
(1a) L-glutamine + H₂O = L-glutamate + NH₃
(1b) ATP + hydrogencarbonate = ADP + carboxyphosphate
(1c) NH₃ + carboxyphosphate = carbamate + phosphate
(1d) ATP + carbamate = ADP + carbamoyl phosphate

For diagram of pyrimidine biosynthesis, click here

Other name(s):

carbamoyl-phosphate synthetase (glutamine-hydrolysing); carbamyl phosphate synthetase (glutamine); carbamoylphosphate synthetase II; glutamine-dependent carbamyl phosphate synthetase; carbamoyl phosphate synthetase; CPS; carbon-dioxide:L-glutamine amido-ligase (ADP-forming, carbamate-phosphorylating); carA (gene name); carB (gene name); CAD (gene name); hydrogen-carbonate:L-glutamine amido-ligase (ADP-forming, carbamate-phosphorylating)

Systematic name:

hydrogencarbonate:L-glutamine amido-ligase (ADP-forming, carbamate-phosphorylating)

Comments:

The product carbamoyl phosphate is an intermediate in the biosynthesis of arginine and the pyrimidine nucleotides [4]. The enzyme from Escherichia coli has three separate active sites, which are connected by a molecular tunnel that is almost 100 Å in length [8]. The amidotransferase domain within the small subunit of the enzyme hydrolyses glutamine to ammonia via a thioester intermediate. The ammonia migrates through the interior of the protein, where it reacts with carboxyphosphate to produce the carbamate intermediate. The carboxyphosphate intermediate is formed by the phosphorylation of hydrogencarbonate by ATP at a site contained within the N-terminal half of the large subunit. The carbamate intermediate is transported through the interior of the protein to a second site within the C-terminal half of the large subunit, where it is phosphorylated by another ATP to yield the final product, carbamoyl phosphate [6]. cf. EC 6.3.4.16, carbamoyl-phosphate synthase (ammonia).

Links to other databases:

BRENDA, EXPASY, Gene, KEGG, MetaCyc, PDB, CAS registry number: 37233-48-0

References:

1.	Anderson, P.M. and Meister, A. Evidence for an activated form of carbon dioxide in the reaction catalysed by Escherichia coli carbamyl phosphate synthetase. Biochemistry 4 (1965) 2803–2809. [PMID: 5326356]
2.	Kalman, S.M., Duffield, P.H. and Brzozowski, T. Purification and properties of a bacterial carbamyl phosphate synthetase. J. Biol. Chem. 241 (1966) 1871–1877. [PMID: 5329589]
3.	Yip, M.C.M. and Knox, W.E. Glutamine-dependent carbamyl phosphate synthetase. Properties and distribution in normal and neoplastic rat tissues. J. Biol. Chem. 245 (1970) 2199–2204. [PMID: 5442268]
4.	Stapleton, M.A., Javid-Majd, F., Harmon, M.F., Hanks, B.A., Grahmann, J.L., Mullins, L.S. and Raushel, F.M. Role of conserved residues within the carboxy phosphate domain of carbamoyl phosphate synthetase. Biochemistry 35 (1996) 14352–14361. [DOI] [PMID: 8916922]
5.	Holden, H.M., Thoden, J.B. and Raushel, F.M. Carbamoyl phosphate synthetase: a tunnel runs through it. Curr. Opin. Struct. Biol. 8 (1998) 679–685. [DOI] [PMID: 9914247]
6.	Raushel, F.M., Thoden, J.B., Reinhart, G.D. and Holden, H.M. Carbamoyl phosphate synthetase: a crooked path from substrates to products. Curr. Opin. Chem. Biol. 2 (1998) 624–632. [DOI] [PMID: 9818189]
7.	Raushel, F.M., Thoden, J.B. and Holden, H.M. The amidotransferase family of enzymes: molecular machines for the production and delivery of ammonia. Biochemistry 38 (1999) 7891–7899. [DOI] [PMID: 10387030]
8.	Thoden, J.B., Huang, X., Raushel, F.M. and Holden, H.M. Carbamoyl-phosphate synthetase. Creation of an escape route for ammonia. J. Biol. Chem. 277 (2002) 39722–39727. [DOI] [PMID: 12130656]

[EC 6.3.5.5 created 1972 as EC 2.7.2.9, transferred 1978 to EC 6.3.5.5, modified 2006]