Oligosaccharide synthesis by glycosynthases

Oligosaccharide synthesis is becoming increasingly important to the pharmaceutical industry because these biomolecules have potential application as therapeutics. Enzymatic synthesis of oligosaccharides includes both glycosyl transferases and glycosidases. The main advantage of this approach compared with traditional chemical synthesis is the regio- and stereo-selectivity that can be achieved without the need for protecting functional groups. However, the limited availability of glycosyl transferases, the high cost of their substrates, and the poor yields of the synthetic reactions per- formed by the glycosidases hamper their use in the large-scale production of oligosaccharides. The recent advent of glycosynthases – specifically mutated glyco- sidases that efficiently synthesize oligosaccharides but do not hydrolyse them – represents a promising sol- ution to these problems. Here, we review the most recent developments in the glycosynthase approach.