This proposal is focused on characterizing the substrate tolerances of several enzymes in the teicoplanin and A-40,926 biosynthetic pathways. Teicoplanin and A-40,926 are glycopeptide antibiotics that are important therapeutics in the fight against several Gram-positive pathogens including methicillin resistant S. aureus. Derivatives of these antibiotics, particularly modifications of the sugar and acyl residues, have increased biological activity against glycopeptide resistant bacteria. The complexity of these natural products is prohibitive to generating libraries of derivatives so harnessing the biosynthetic machinery to support the chemoenzymatic synthesis is an attractive route towards improved glycopeptides. The glycosyltransferases and acyltransferases from these two pathways have been recently identified. We will assess the potential of these enzymes to be used as combinatorial reagents for synthesizing variants of glycopeptide antibiotics by probing their substrate specificities. Any new glycopeptides that are synthesized will be tested for antimicrobial activity against several bacterial strains.
