IUBMB Enzyme Nomenclature

EC 1.13.11.79

Accepted name: 5,6-dimethylbenzimidazole synthase

Reaction: FMNH2 + O2 = 5,6-dimethylbenzimidazole + D-erythrose 4-phosphate + other product(s)

For diagram of reaction click here.

Other name(s): BluB

Systematic name: FMNH2 oxidoreductase (5,6-dimethylbenzimidazole-forming)

Comments: The enzyme catalyses a complex oxygen-dependent conversion of reduced flavin mononucleotide to form 5,6-dimethylbenzimidazole, the lower ligand of vitamin B12. This conversion involves many sequential steps in two distinct stages, and an alloxan intermediate that acts as a proton donor, a proton acceptor, and a hydride acceptor [4]. The C-2 of 5,6-dimethylbenzimidazole is derived from C-1' of the ribityl group of FMNH2 and 2-H from the ribityl 1'-pro-S-hydrogen. While D-erythrose 4-phosphate has been shown to be one of the byproducts, the nature of the other product(s) has not been verified yet.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:

References:

1. Gray, M.J. and Escalante-Semerena, J.C. Single-enzyme conversion of FMNH2 to 5,6-dimethylbenzimidazole, the lower ligand of B12. Proc. Natl. Acad. Sci. USA 104 (2007) 2921-2926. [PMID: 17301238]

2. Ealick, S.E. and Begley, T.P. Biochemistry: molecular cannibalism. Nature 446 (2007) 387-388. [PMID: 17377573]

3. Taga, M.E., Larsen, N.A., Howard-Jones, A.R., Walsh, C.T. and Walker, G.C. BluB cannibalizes flavin to form the lower ligand of vitamin B12. Nature 446 (2007) 449. [PMID: 17377583]

4. Wang, X.L. and Quan, J.M. Intermediate-assisted multifunctional catalysis in the conversion of flavin to 5,6-dimethylbenzimidazole by BluB: a density functional theory study. J. Am. Chem. Soc. 133 (2011) 4079-4091. [PMID: 21344938]

[EC 1.13.11.79 created 2010 as EC 1.14.99.40, transferred 2014 to EC 1.13.11.79]


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