Anaerobic 5-Hydroxybenzimidazole Formation from Aminoimidazole Ribotide: An Unanticipated Intersection of Thiamin and Vitamin B₁₂ Biosynthesis.

Comparative genomics of the bacterial thiamin pyrimidine synthase (thiC) revealed a paralogue of thiC (bzaF) clustered with anaerobic vitamin B12 biosynthetic genes. Here we demonstrate that BzaF is a radical S-adenosylmethionine enzyme that catalyzes the remarkable conversion of aminoimidazole ribotide (AIR) to 5-hydroxybenzimidazole (5-HBI). We identify the origin of key product atoms and propose a reaction mechanism. These studies represent the first step in solving a long-standing problem in anaerobic vitamin B12 assembly and reveal an unanticipated intersection of thiamin and vitamin B12 biosynthesis.

[1]  Non-canonical active site architecture of the radical SAM thiamin pyrimidine synthase , 2015, Nature communications.

[2]  S. Thore,et al.  High-resolution crystal structure of the eukaryotic HMP-P synthase (THIC) from Arabidopsis thaliana. , 2013, Journal of structural biology.

[3]  Tadhg P Begley,et al.  A "radical dance" in thiamin biosynthesis: mechanistic analysis of the bacterial hydroxymethylpyrimidine phosphate synthase. , 2010, Angewandte Chemie.

[4]  C. Krebs,et al.  Reconstitution of ThiC in thiamine pyrimidine biosynthesis expands the radical SAM superfamily. , 2008, Nature chemical biology.

[5]  W. K. Wilson,et al.  An oxidosqualene cyclase makes numerous products by diverse mechanisms: a challenge to prevailing concepts of triterpene biosynthesis. , 2007, Journal of the American Chemical Society.

[6]  C. Walsh,et al.  BluB cannibalizes flavin to form the lower ligand of vitamin B12 , 2007, Nature.

[7]  R. Mehl,et al.  Biosynthesis of the thiamin pyrimidine: the reconstitution of a remarkable rearrangement reaction. , 2004, Organic & biomolecular chemistry.

[8]  A. Scott,et al.  Discovering nature's diverse pathways to vitamin B12: a 35-year odyssey. , 2003, The Journal of organic chemistry.

[9]  D. Cane,et al.  Trichodiene synthase. Probing the role of the highly conserved aspartate-rich region by site-directed mutagenesis. , 1996, Biochemistry.

[10]  P. Renz,et al.  7-Azabenzimidazolylcobamide and 5,6-dimethyl-7-azabenzimidazolylcobamide, new vitamin B12-analogs synthesized from 4(5)-aminoimidazole by Eubacterium limosum. , 1995, Biological chemistry Hoppe-Seyler.

[11]  J. Marquart,et al.  Biosynthesis of vitamin B12 in anaerobic bacteria. Transformation of 5-hydroxybenzimidazole and 5-hydroxy-6-methylbenzimidazole into 5,6-dimethylbenzimidazole in Eubacterium limosum. , 1993, European journal of biochemistry.

[12]  J. Vogt,et al.  Biosynthesis of vitamin B12 in anaerobic bacteria. Experiments with Eubacterium limosum on the incorporation of D-[1-13C]erythrose and [13C]formate into the 5,6-dimethylbenzimidazole moiety. , 1992, European journal of biochemistry.

[13]  E. Myers,et al.  Basic local alignment search tool. , 1990, Journal of molecular biology.

[14]  J. Vogt,et al.  Biosynthesis of vitamin B-12 in anaerobic bacteria. Experiments with Eubacterium limosum on the origin of the amide groups of the corrin ring and of N-3 of the 5,6-dimethylbenzimidazole part. , 1988, European journal of biochemistry.

[15]  K. Yamada,et al.  Precursor of carbon atom five and hydroxymethyl carbon atom of the pyrimidine moiety of thiamin in Escherichia coli. , 1983, Journal of nutritional science and vitaminology.