Reaction: 2 ATP + L-glutamine + HCO3- + H2O = 2 ADP + phosphate + L-glutamate + carbamoyl phosphate (overall reaction)
(1a) L-glutamine + H2O = L-glutamate + NH3
(1b) ATP + HCO3- = ADP + carboxyphosphate
(1c) NH3 + carboxyphosphate = carbamate + phosphate
(1d) ATP + carbamate = ADP + carbamoyl phosphate
For diagram of reaction 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)
Systematic name: HCO3-: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 . The enzyme from Escherichia coli has three separate active sites, which are connected by a molecular tunnel that is almost 100 Å in length . 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 carboxy phosphate to produce the carbamate intermediate. The carboxy-phosphate intermediate is formed by the phosphorylation of bicarbonate 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 .
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 37233-48-0
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