Anaerobic 5-Hydroxybenzimidazole Formation from Aminoimidazole Ribotide: An Unanticipated Intersection of Thiamin and Vitamin B<sub>12</sub> Biosynthesis
作者:Angad P. Mehta、Sameh H. Abdelwahed、Michael K. Fenwick、Amrita B. Hazra、Michiko E. Taga、Yang Zhang、Steven E. Ealick、Tadhg P. Begley
DOI:10.1021/jacs.5b03576
日期:2015.8.26
(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
Biosynthesis of the thiamin pyrimidine: the reconstitution of a remarkable rearrangement reaction
作者:Brian G. Lawhorn、Ryan A. Mehl、Tadhg P. Begley
DOI:10.1039/b405429f
日期:——
The conversion of 5-aminoimidazole ribonucleotide (AIR) into 4-amino-2-methyl-5-hydroxymethylpyrimidine (HMP) is a fascinating reaction on the thiamin biosynthetic pathway in bacteria and is probably the most complex unresolved rearrangement in primary metabolism. We have successfully reconstituted this reaction in a cell-free system. The E. coli thiC gene product and an additional unidentified E. coli protein are required for the reaction. In addition, SAM and nicotinamide cofactors are required for full activity. Labeling studies to determine the origin of most of the atoms in the pyrimidine are described. Based on these studies, a new mechanism for HMP formation is proposed.
A “Radical Dance” in Thiamin Biosynthesis: Mechanistic Analysis of the Bacterial Hydroxymethylpyrimidine Phosphate Synthase
作者:Abhishek Chatterjee、Amrita B. Hazra、Sameh Abdelwahed、David G. Hilmey、Tadhg P. Begley
DOI:10.1002/anie.201003419
日期:2010.11.8
Tricky things with ThiC: Hydroxymethylpyrimidinephosphate (HMP‐P) synthase (ThiC) catalyzes one of the most complex rearrangement reactions in primary metabolism. Deuteration experiments show that under reducing conditions, in the presence of aminoimidazole ribonucleotide, the 5′‐deoxyadenosyl radical generated at the active site of ThiC reacts directly with the substrate and performs two iterative