The Active Site Sulfenic Acid Ligand in Nitrile Hydratases Can Function as a Nucleophile

Document Type

Article

Language

eng

Format of Original

4 p.

Publication Date

1-29-2014

Publisher

American Chemical Society

Source Publication

Journal of the American Chemical Society

Source ISSN

0002-7863

Original Item ID

DOI: 10.1021/ja410462j

Abstract

Nitrile hydratase (NHase) catalyzes the hydration of nitriles to their corresponding commercially valuable amides at ambient temperatures and physiological pH. Several reaction mechanisms have been proposed for NHase enzymes; however, the source of the nucleophile remains a mystery. Boronic acids have been shown to be potent inhibitors of numerous hydrolytic enzymes due to the open shell of boron, which allows it to expand from a trigonal planar (sp2) form to a tetrahedral form (sp3). Therefore, we examined the inhibition of the Co-type NHase from Pseudonocardia thermophila JCM 3095 (PtNHase) by boronic acids via kinetics and X-ray crystallography. Both 1-butaneboronic acid (BuBA) and phenylboronic acid (PBA) function as potent competitive inhibitors of PtNHase. X-ray crystal structures for BuBA and PBA complexed to PtNHase were solved and refined at 1.5, 1.6, and 1.2 Å resolution. The resulting PtNHase–boronic acid complexes represent a “snapshot” of reaction intermediates and implicate the cysteine-sulfenic acid ligand as the catalytic nucleophile, a heretofore unknown role for the αCys113–OH sulfenic acid ligand. Based on these data, a new mechanism of action for the hydration of nitriles by NHase is presented.

Comments

Published version. Journal of the American Chemical Society, Vol. 136, No. 4 (January 29, 2014): 1186-1189. DOI. © 2014 American Chemical Society. Used with permission.

ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.

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