4jd5

Publication Abstract from PubMed

It is widely accepted that, in thiamin diphosphate (ThDP)-dependent enzymes, much of the rate acceleration is provided by the cofactor. Inter alia, the reactive conformation of ThDP, known as the V-conformation, has been attributed to the presence of a bulky hydrophobic residue located directly below the cofactor. Here we report the use of site-saturation mutagenesis to generate variants of this residue (Leu403) in benzoylformate decarboxylase. The observed 3 orders of magnitude range in kcat/Km values suggested that conformational changes in the cofactor could be influencing catalysis. However, X-ray structures of several variants were determined, and there was remarkably little change in ThDP conformation. Rather, it seemed that, once the V-conformation was attained, residue size and hydrophobicity were more important for enzyme activity.

A bulky hydrophobic residue is not required to maintain the v-conformation of enzyme-bound thiamin diphosphate.,Andrews FH, Tom AR, Gunderman PR, Novak WR, McLeish MJ Biochemistry. 2013 May 7;52(18):3028-30. doi: 10.1021/bi400368j. Epub 2013 Apr, 23. PMID:23607689^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.