Nitrile hydratases (NHases): At the interface of academia and industry

Nitrile hydratase (NHase, EC 4.2.1.84) is one of the key enzymes of nitrile metabolism in a large number of microbes that catalyses the hydration of nitriles to corresponding amides, and has been successfully adopted in chemical industry for production of acrylamide, nicotinamide and 5-cyanovaleramide. However, NHase is still under active consideration of enzymologists to expand its potential for synthesis of various amides. Most of the NHases have been reported for their limited substrates acceptability, low enantioselectivity and thermostability and therefore a considerable improvement is required for developing as robust biocatalyst for synthesis of a range of organic amides. Studies on biochemical properties, gene configuration, active-site chemical models and site-directed mutagenesis have given the insight into the structural and functional characteristics of NHase. Keeping in view, the present review critically describes the available information on natural sources (based on activity and phylogenetic analysis), biochemical properties, catalysis–structure relationship, molecular expression and potential applications of this enzyme.