Glycosynthases in Biocatalysis

Glycosynthases, engineered glycoside hydrolases that are able to synthesize glycans in quantitative yields without hydrolyzing them, are among the most interesting tools for the chemoenzymatic synthesis of carbohydrates that have been made available so far. From their invention in 1998, these enzymes have been developed enormously and demonstrated to be convenient alternatives to the more expensive glycosyltransferase. Glycosynthases have been proved to be efficient catalysts for the synthesis of oligosaccharides, polysaccharides, and glycoconjugates of various lengths containing different monosaccharides bound through alpha- and beta-linkages, which have interesting applications. In this review we describe the impact that glycosynthases have had on the biocatalysis and biosynthesis of carbohydrates through the description of the novel activities produced and of the development of the glycosynthase-based process. In addition, we summarize the approaches that, according to the current literature, can be adopted to produce novel glycosynthase activities and to improve the existing process.