Modern Approaches to Discovering New Hydroxynitrile Lyases for Biocatalysis

Hydroxynitrile lyases (HNLs) have grown in importance from laboratory to industry due to their potential to catalyze stereoselective C-C bond-formation reactions in the synthesis of several chiral intermediates, such as enantiopure α-cyanohydrins, β-nitro alcohols, and their derivatives with multiple functional groups. With these wide applications, the demand for finding new HNLs has increased, and this has led to exploration not only of new HNLs but also of new ways to discover them. An exclusive review article on HNLs by Asano et al. in 2011 described the discovery of HNLs along with their applications. Since then many scientific advancements have been seen in this area. This article aims to highlight the modern HNL discovery approaches, based mainly on 1) genome mining, 2) use of INTMSAlign software, 3) rational design (based on a millipede HNL), 4) evolution of catalytic mechanisms, 5) protein engineering guided by catalytic mechanisms, and 6) screening of plants with cyanogen glycoside (CG) content. This description is followed by future prospects. Overall this review represents the present state and the future potential of HNL discovery approaches, and so might be hoped to be instrumental not only in exploration of new HNLs but also in the invention of methods for potential biotechnological applications.