Hydroxynitrile lyases: At the interface of biology and chemistry

Hydroxynitrile lyases are the versatile group of enzymes, which play a significant defensive role in plant system against microbial attack. In chemical industries, hydroxynitrile lyase is used as an important industrial biocatalyst for the synthesis of chiral cyanohydrins by exploiting the reversible enzymatic reaction. Cyanohydrins are biologically active compounds used in synthesis of β-amino alcohols, α-hydroxy ketones and α-hydroxy acids, which have importance as fine chemicals, pharmaceuticals and agrochemicals. NMR and inhibition studies reveled the involvement of different amino acids at the active site and proved that the hydroxynitrile lyases generally utilize acid/base catalysis mechanism. Protein engineering and site directed mutagenesis have been used to change the active site and alter the substrate specificity of various hydroxynitrile lyases. Many recombinant hydroxynitrile lyases have been expressed in Escherichia coli, Saccharomyces cerevisiae and Pichia pastoris.