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

Citation:
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 (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)
1
Cobalt-containing Nitrile Hydratase Subunit Alpha
Molecule annotation
1
Cobalt-containing Nitrile Hydratase Subunit Beta
Molecule annotation
Chemicals (2 molecules)
1
1
2
1
* Click molecule labels to explore molecular sequence information.

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