5 (carboxyamino)imidazole ribonucleotide synthase

In enzymology, a 5-(carboxyamino)imidazole ribonucleotide synthase (EC 6.3.4.18) is an enzyme that catalyzes the chemical reaction

ATP + 5-amino-1-(5-phospho-D-ribosyl)imidazole + HCO₃⁻ ⇌ ADP + phosphate + 5-carboxyamino-1-(5-phospho-D-ribosyl)imidazole

The 3 substrates of this enzyme are ATP, 5-amino-1-(5-phospho-D-ribosyl)imidazole ("AIR"), and HCO₃⁻, whereas its 3 products are ADP, phosphate, and 5-carboxyamino-1-(5-phospho-D-ribosyl)imidazole.

This enzyme belongs to the family of ligases, specifically those forming generic carbon-nitrogen bonds. The systematic name of this enzyme class is 5-amino-1-(5-phospho-D-ribosyl)imidazole:carbon-dioxide ligase (ADP-forming). Other names in common use include N5-CAIR synthetase, N5-carboxyaminoimidazole ribonucleotide synthetase, and PurK.