5-(carboxyamino)imidazole ribonucleotide mutase (PurE (also known as N5-CAIR mutase))

5-(carboxyamino)imidazole ribonucleotide mutase—commonly referred to as PurE or N5-carboxyaminoimidazole ribonucleotide mutase—is an enzyme classified under EC 5.4.99.18 that catalyzes a key step in the de novo purine biosynthetic pathway in bacteria, fungi, and plants[1][2]. Specifically, it mediates the reversible conversion between N5-carboxyaminoimidazole ribonucleotide (N5-CAIR) and 4-carboxy-aminoimidazole ribonucleotide (CAIR), a reaction not found in humans who use a different enzyme for this transformation[6][9]. This distinction makes PurE an attractive target for selective antimicrobial drug development because its inhibition could disrupt purine synthesis specifically in microbes without affecting human cells[6][9]. Structural studies have revealed important catalytic residues such as histidine that are essential for its function; mechanistic insights suggest direct CO₂ transfer during catalysis with proton transfers facilitated by conserved amino acids like His45 or His59 depending on species[4][8]. No approved drugs currently target this enzyme directly; however, it is actively studied as a potential antibacterial target due to its absence from human metabolism and essentiality for microbial growth[6][9].

Other names

N5-carboxyaminoimidazole ribonucleotide mutaseN5-CAIR mutasePurEclass I PurE5-carboxyamino-1-(5-phospho-D-ribosyl)imidazole carboxymutase[1][2]