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EC 6.3.4.16 Details
EC number
6.3.4.16
Accepted name
carbamoyl-phosphate synthase (ammonia)
Reaction
2 ATP + NH3 + hydrogencarbonate = 2 ADP + phosphate + carbamoyl phosphate (overall reaction);;(1a) ATP + hydrogencarbonate = ADP + carboxyphosphate;;(1b) NH3 + carboxyphosphate = carbamate + phosphate;;(1c) ATP + carbamate = ADP + carbamoyl phosphate
Other name(s)
carbon-dioxide—ammonia ligase, carbamoylphosphate synthase, carbamylphosphate synthetase, carbamoylphosphate synthase (ammonia), carbamoylphosphate synthetase, carbamylphosphate synthetase I, CPSI (gene name), carbon-dioxide:ammonia ligase (ADP-forming, carbamate-phosphorylating)
Systematic name
hydrogencarbonate:ammonia ligase (ADP-forming, carbamate-phosphorylating)
CAS registry number
9026-23-7
Comment
The enzyme catalyses the first committed step in the urea cycle. The reaction proceeds via three separate chemical reactions: phosphorylation of hydrogencarbonate to carboxyphosphate; a nucleophilic attack of ammonia on carboxyphosphate yielding carbamate; and the phosphorylation of carbamate forming carbamoyl phosphate. Two moles of ATP are utilized for the synthesis of one molecule of carbamyl phosphate, making the reaction essentially irreversible. The enzyme requires the allosteric activator N-acetyl-L-glutamate. cf. EC 6.3.5.5, carbamoyl-phosphate synthase (glutamine-hydrolysing).
History
created 1965 as EC 2.7.2.5, transferred 1978 to EC 6.3.4.16
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EC Tree
1 Oxidoreductases
1.1 Acting on the CH-OH group of donors
1.2 Acting on the aldehyde or oxo group of donors
1.2.1 With NAD+ or NADP+ as acceptor
1.2.2 With a cytochrome as acceptor
1.2.3 With oxygen as acceptor
1.2.4 With a disulfide as acceptor
1.2.5 With a quinone or similar compound as acceptor
1.2.7 With an iron-sulfur protein as acceptor
1.2.98 With other, known, physiological acceptors
1.2.99 With unknown physiological acceptors
1.3 Acting on the CH-CH group of donors
1.4 Acting on the CH-NH2 group of donors
1.5 Acting on the CH-NH group of donors
1.6 Acting on NADH or NADPH
1.7 Acting on other nitrogenous compounds as donors
1.8 Acting on a sulfur group of donors
1.9 Acting on a heme group of donors
1.10 Acting on diphenols and related substances as donors
1.11 Acting on a peroxide as acceptor
1.12 Acting on hydrogen as donor
1.13 Acting on single donors with incorporation of molecular oxygen (oxygenases)
1.14 Acting on paired donors, with incorporation or reduction of molecular oxygen
1.15 Acting on superoxide as acceptor
1.16 Oxidizing metal ions
1.17 Acting on CH or CH2 groups
1.18 Acting on iron-sulfur proteins as donors
1.19 Acting on reduced flavodoxin as donor
1.20 Acting on phosphorus or arsenic in donors
1.21 Catalysing the reaction X-H + Y-H = X-Y
1.21.1 With NAD+ or NADP+ as acceptor
1.21.3 With oxygen as acceptor
1.21.4 With a disulfide as acceptor
1.21.98 With other, known, physiological acceptors
1.21.99 With unknown physiological acceptors
1.22 Acting on halogen in donors
1.23 Reducing C-O-C group as acceptor
1.97 Other oxidoreductases
1.98 Enzymes using H2 as reductant (deleted subclass)
1.98.1. undefined
1.99 Other enzymes using O2 as oxidant (deleted subclass)
2 Transferases
3 Hydrolases
4 Lyases
5 Isomerases
6 Ligases
6.1 Forming carbon-oxygen bonds
6.2 Forming carbon-sulfur bonds
6.3 Forming carbon-nitrogen bonds
6.3.1 Acid—ammonia (or amine) ligases (amide synthases)
6.3.2 Acid—amino-acid ligases (peptide synthases)
6.3.3 Cyclo-ligases
6.3.4 Other carbon-nitrogen ligases
6.3.4.1 GMP synthase
6.3.4.2 CTP synthase (glutamine hydrolysing)
6.3.4.3 formate—tetrahydrofolate ligase
6.3.4.4 adenylosuccinate synthase
6.3.4.5 argininosuccinate synthase
6.3.4.6 urea carboxylase
6.3.4.7 ribose-5-phosphate—ammonia ligase
6.3.4.8 imidazoleacetate—phosphoribosyldiphosphate ligase
6.3.4.9 biotin—[methylmalonyl-CoA-carboxytransferase] ligase
6.3.4.10 biotin—[propionyl-CoA-carboxylase (ATP-hydrolysing)] ligase
6.3.4.11 biotin—[methylcrotonoyl-CoA-carboxylase] ligase
6.3.4.12 glutamate—methylamine ligase
6.3.4.13 phosphoribosylamine—glycine ligase
6.3.4.14 biotin carboxylase
6.3.4.15 biotin—[biotin carboxyl-carrier protein] ligase
6.3.4.16 carbamoyl-phosphate synthase (ammonia)
6.3.4.17 formate—dihydrofolate ligase
6.3.4.18 5-(carboxyamino)imidazole ribonucleotide synthase
6.3.4.19 tRNAIle-lysidine synthase
6.3.4.20 7-cyano-7-deazaguanine synthase
6.3.4.21 nicotinate phosphoribosyltransferase
6.3.4.22 tRNAIle2-agmatinylcytidine synthase
6.3.4.23 formate—phosphoribosylaminoimidazolecarboxamide ligase
6.3.4.24 tyramine—L-glutamate ligase
6.3.4.25 2-amino-2′-deoxyadenylo-succinate synthase
6.3.5 Carbon-nitrogen ligases with glutamine as amido-N-donor
6.4 Forming carbon-carbon bonds
6.5 Forming phosphoric-ester bonds
6.6 Forming nitrogen—metal bonds
6.7 Forming nitrogen-nitrogen bonds
7 Translocases