Recent advances in the oligosaccharide synthesis promoted by catalytically engineered glycosidases

In oligosaccharide synthesis the chemo-enzymatic approach is often chosen to obtain the desired glycosidic bond by exploiting the exquisite substrate specificity and stereoselectivity of glycosidases and glycosyltransferases. In recent years the invention of new enzymatic activities, named glycosynthases, created a third route for the enzymatic synthesis of oligosaccharides. Glycosynthases are mutant glycosidases, devoid of hydrolytic activity, that produce oligosaccharides with yields >80%. The glycosynthase technology is now well established and was greatly improved recently. Several groups experimentally proved that this methodology can be applied to several glycosidases and that the activity of existing glycosynthases can be significantly enhanced. In this review we briefly describe the characteristics of these synthetic tools and show a survey of the most recent findings. Methods for the prediction of the glycosynthetic potential of known glycosidases are also discussed.