Synthesis and modifications of carbohydrates, using biotransformations

Enzymes continue to be used as important catalysts, for the generation of rare and 'unnatural' monosaccharides and for the selective formation of glycosidic linkages. Multi-enzyme systems have been employed in one-pot strategies for multistep reaction sequences and for co-factor regeneration. The efficiency of glycosidases for glycosylation reactions has been dramatically increased by active-site mutagenesis to generate glycosynthases. First reports have detailed the expansion and optimization of glycosynthase substrate specificity by directed evolution. Novel glycosyltransferases are being identified from genomic databases and have been shown to glycosylate complex metabolites, such as glycopeptide antibiotics, with exquisite selectivity and in good yields. An emerging field is the application of glycosynthases and glycosyltransferases to reactions on solid support, generating potential applications in microarrays.