The carbamoyl-phosphate synthase domain is in the amino terminus of protein. Carbamoyl-phosphate synthase catalyses the ATP-dependent synthesis of carbamyl-phosphate from glutamine or ammonia and bicarbonate. This important enzyme initiates both the urea cycle and the biosynthesis of arginine and/or pyrimidines [1]. The carbamoyl-phosphate synthase (CPS) enzyme in prokaryotes is a heterodimer of a small and large chain. The small chain promotes the hydrolysis of glutamine to ammonia, which is used by the large chain to synthesise carbamoyl phosphate. See Pfam:PF00289. The small chain has a GATase domain in the carboxyl terminus. See Pfam:PF00117.

1: Mammalian carbamyl phosphate synthetase (CPS). DNA sequence and evolution of the CPS domain of the Syrian hamster multifunctional protein CAD. Simmer JP, Kelly RE, Rinker AG Jr, Scully JL, Evans DR; Biol Chem 1990;265:10395-10402. PMID:1972379