-!- 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 A in length. -!- The amidotransferase domain within the small subunit of the enzyme hydrolyzes 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. -!- Cf. EC 6.3.4.16. -!- Formerly EC 2.7.2.9.