Chemical biology tools for studying carbohydrate processing enzymes

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The modification of proteins with sugars is known as protein glycosylation and is a common modification of cellular proteins in all kingdoms of life. Glycosylation is particularly abundant in multicellular eukaryotes, where over half of all proteins are thought to be modified by sugars linked together for form what are known as glycans. The dedication of approximately 300 genes within the human genome to the regulation of glycoconjugates highlights the important roles played by these species. The enzymes responsible for building of glycoconjugates are glycosyltransferases and those that break them down are known as glycosidases. The importance of these enzymes rests in the roles they play in regulating the structures and abundance of glycoconjugates, which have been found to alter protein function, mediate molecular interactions, and alter the stability of proteins. Striking findings in the past few years have also shown that protein glycosylation acts directly to regulate signaling and transcription. Recently, the National Academy of Sciences and National Research Council (USA) identified the area of glycoscience as a promising and emerging area of research that merits significant investment. Indeed, the field of protein glycosylation lags somewhat behind the study of other, more prominent, classes of biomolecules such as phosphorylation. Several reasons to account for this difference in progress have been made. Among the rationales proposed is that there is a limited repertoire of chemical tools available that can be used by the wider research community to study relevant glycans structures as well as the enzymes that process these species. To address this gap, a major thrust of our research program is directed toward developing chemical tools that will greatly facilitate research into understanding less appreciated and poorly understood forms of eukaryotic protein glycosylation. In this proposal we outlined a principally carbohydrate chemistry and enzymology-based program of research comprising three aims. We will create probes to monitor glycosidase and glycosyltransferase and to create inhibitors of these enzymes. The molecules resulting from these efforts will be validated in cells to identify those which are active in cells. The resulting new chemical tools will enable the field to improve our understanding of how the enzymes that regulate these glycan structures function within cells. The tools developed here should therefore help access knowledge that could help researchers in other fields develop new diagnostics or therapeutics.