Nicotinate-nucleotide--dimethylbenzimidazole phosphoribosyltransferase (CobT)

Nicotinate-nucleotide--dimethylbenzimidazole phosphoribosyltransferase (EC 2.4.2.21), also known as CobT, is an enzyme that catalyzes the phosphoribosyltransfer reaction essential for the biosynthesis of cobalamin (vitamin B12) in bacteria. It converts beta-nicotinate D-ribonucleotide and 5,6-dimethylbenzimidazole into alpha-ribazole-5'-phosphate, a key intermediate for assembling the nucleotide loop of cobalamin. CobT is a glycosyltransferase of the pentosyltransferase family and plays a central role in the anaerobic pathway of vitamin B12 production. Structurally, CobT is a dimer with each subunit featuring a Rossmann fold and a three-helix bundle domain. The enzyme’s active site forms a hydrophobic pocket accommodating the substrate 5,6-dimethylbenzimidazole, and it undergoes a disorder-to-order transition upon substrate binding. It is distinct in structure from other phosphoribosyltransferases, and its function is crucial for bacterial metabolism but not directly linked to human enzymes or diseases[1][2][4][7][10].

Other names

Nicotinate mononucleotide-dimethylbenzimidazole phosphoribosyltransferaseNicotinate ribonucleotide:benzimidazole (adenine) phosphoribosyltransferaseNicotinate mononucleotide (NaMN):5,6-dimethylbenzimidazole phosphoribosyltransferaseCobT