EC Explorer

4.1.99.23

5-hydroxybenzimidazole synthase

5-amino-1-(5-phospho-β-D-ribosyl)imidazole + S-adenosyl-L-methionine + reduced acceptor = 5-hydroxybenzimidazole + 5′-deoxyadenosine + L-methionine + formate + NH₃ + phosphate + oxidized acceptor

bzaF (gene name), HBI synthase

5-amino-1-(5-phospho-β-D-ribosyl)imidazole formate-lyase (5-hydroxybenzimidazole-forming)

The enzyme, purified from bacteria, is part of the anaerobic pathway for cobalamin biosynthesis. It binds a [4Fe-4S] cluster that is coordinated by 3 cysteines and an exchangeable S-adenosyl-L-methionine molecule. The first stage of catalysis is reduction of the S-adenosyl-L-methionine to produce L-methionine and a 5′-deoxyadenosin-5′-yl radical that is crucial for the conversion of the substrate.

created 2017