Development, Production, and Application of Recombinant Yeast Biocatalysts in Organic Synthesis

The use of biocatalysts from yeast strains in organic synthesis is well established and covers a broad range of reaction classes. A particularly interesting reaction class is the regio- and stereospecific attachment of sugar moieties (i.e. glycosylation) to a variety of natural products, from small molecules up to oligosaccharides and proteins. Since the bioactivity of many therapeutics depends on the proper glycosylation, the improvement of glycosylation methodology by chemical synthesis, biocatalysis or in vivo approaches is of major interest. We have developed glycosyltransferase-toolkits for the straight-forward and quantitative transfer of a specific monosaccharide moiety to an acceptor substrate. The stable expression of the ?(1?4)-galactosyltransferase I in Saccharomyces cerevisiae and ?(1?3)-fucosyltransferase VI in Pichia pastoris has enabled these biocatalysts to be prepared in large-scale for use in organic synthesis. The application of galactosyltransferase using UDP-galactose and fucosyltransferase using GDP-fucose as NDP-sugar donor in the regio- and stereospecific galactosylation and fucosylation of small molecules is shown with a simplified reaction system. Optimisation of the reaction conditions allows for quantitative glycosylation reactions. The use of recombinant yeasts has been the key to performing this highly efficient glycosylation methodology and represents a building block of biocatalytic glycomics for the future