Modular Synthesis of N-Glycans and Homogeneous Glycoproteins

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The Chemical Synthesis Program of the Chemistry Division supports the project led by Professor Chi-Huey Wong at The Scripps Research Institute. His group focuses on the development of a new combination of chemical and enzymatic methods for the synthesis of complex oligosaccharides to be attached to proteins to form homogeneous glycoproteins such as antibodies. Most of the proteins in humans and other higher organisms have various sugars attached to form a heterogeneous population of glycoproteins. As a result, it has been difficult to understand the roles sugars play in glycoproteins. This project establishes effective methods for the synthesis of complex oligosaccharides and their use in the assembly of homogeneous glycoproteins containing well defined oligosaccharide structures. Access to these homogeneous glycoproteins allows us to understand how the oligosaccharide affects the functions of proteins and how to make better glycoproteins as medicines or as reagents. This multidisciplinary project presents a rich environment for the training of young scientists.Understanding the effect of glycosylation on protein folding, structure and function is vitally important in biology and medicine and requires access to a large number of complex N- glycans. These oligosaccharides could be assembled using the modular method described in the project, which breaks down the task of N-glycans synthesis into the chemoenzymatic preparation of branched modules and the chemical synthesis of the core unit. The synthesis of branched modules (Specific Aim 1) begins with seven synthetic intermediates, which can be diversified using enzymatic transformations to generate a number of modules. Chemical synthesis of the core oligosaccharide is being optimized to provide N-glycans tailored to a specific application, therefore increasing the utility of this method (Specific Aim 2). Using the synthetic N-glycan samples, new glycoforms of a representative monoclonal antibody are being prepared for the study of their activities (Specific Aim 3). All modules, enzymes, and reagents developed in this study are made available to the community to facilitate our understanding of protein glycosylation and to advance the research in glycoscience.