Biochemistry and Biotechnology of Nitrile Degrading Enzyme Systems from Mesophilic and Thermophilic Bacteria
D.A. COWAN*
Department of Biochemistry and Molecular Biology, Gower St., London WC1E 6BT, U.K.
The nitrile hydratase catalysed conversion of acrylic acid to acrylamide is one of relatively few examples of successfully commercialised large-scale biotransformations. However, the broad specificity of many nitrile hydratases and nitrilases, catalysing the conversion of nitriles to amides and acids respectively, offers a convenient route to the production of diverse chiral intermediates. While the conversion of nitriles to amides and acids can be achieved relatively easily by chemical methods, the enzymic conversion is particularly appropriate where the substrate contains other reactive moieties. The current status and future potential of nitrile biotransformations will be reviewed.
The relative instability of the mesophilic nitrile-degrading enzyme systems has led to a search for thermophilic homologues and several different thermophilic nitrile degrading enzymes have now been reported. At a functional level, these enzymes appear to be closely related to their mesophilic homologues. Both aromatic-specific nitrilases and aliphatic-specific hydratase/amidase systems have been identified. The production, purification and properties of several novel thermophilic nitrile-degrading enzyme systems will be presented. A process for the inhibition of intracellular amidase activity suitable for the whole cell conversion of nitriles to amides is discussed.
