Chemoenzymatic modifications of the carbohydrate moieties on residue 4 and 6 of glycopeptide have great potential in generating new therapeutics against life-threatening vancomycin-resistant pathogens. However, the studies on the attachment of a variety of sugars at residue 6 of the heptapeptide have not been explored. To facilitate the appendage of various sugars at this position, a teicoplanin enzyme tGtfA will be expressed and purified. Its substrate preference will be studied so that it may be used as a potential catalyst to transfer various carbohydrates to the heptapeptide scaffolds. Moreover, chimeric glycosyltransferase with novel activities will be engineered based on the known structures of glycosyltransferases involved in glycopeptide biosynthesis. In addition, reductive alkylation of two triglycosylated glycopeptides will be carried out not only for discovering new antibiotics but also for improving the efficiency of the chemoenzymatic synthesis of glycopeptide variants.
