4OB3: Crystal Structure Of Nitrile Hydratase From Pseudonocardia Thermophila : A Reference Structure To Boronic Acid Inhibition Of Nitrile Hydratase

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 (sp(2)) form to a tetrahedral form (sp(3)). 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 A 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 alphaCys(113)-OH sulfenic acid ligand. Based on these data, a new mechanism of action for the hydration of nitriles by NHase is presented.
PDB ID: 4OB3Download
MMDB ID: 125029
PDB Deposition Date: 2014/1/6
Updated in MMDB: 2014/11
Experimental Method:
x-ray diffraction
Resolution: 1.92  Å
Source Organism:
Similar Structures:
Biological Unit for 4OB3: dimeric; determined by author and by software (PISA)
Molecular Components in 4OB3
Label Count Molecule
Proteins (2 molecules)
Cobalt-containing Nitrile Hydratase Subunit Alpha
Molecule annotation
Cobalt-containing Nitrile Hydratase Subunit Beta
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

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