Chemoenzymatic Synthesis of Glycans and Glycoconjugates

Glycosyltransferases are the biosynthetic enzymes responsible for the construction of interglycosidic linkages and glycosidases catalyze the opposite reaction, hydrolysis of interglycosidic linkages. The diversity of natural glycans is reflected by the numerous glycosyltransferases and glycosidases encountered in nature, each exhibiting a defined substrate specificity. Natural glycans are often encountered in heterogeneous form and often produced in minute amounts making their isolation and characterization from natural sources often cumbersome. Therefore, glycobiology relies heavily on synthetic glycans, and synthetic methodology to produce glycans has witnessed tremendous progress (see Chapter 53). Glycosyltransferases and glycosidases offer advantages in the construction of glycans as these biocatalysts are very powerful under controlled conditions. This chapter summarizes recent developments in the use of (mutant) glycosidases and glycosyltransferases for the synthesis of tailored glycans, including combinations of both enzyme classes and in conjunction with chemically synthesized intermediates are presented.