Oligosaccharides, glycoproteins, and other glycoconjugates are involved in a number of biochemical processes, particularly at the cell surface. Additionally, many disease states, such as cancerous and inflammatory conditions, are associated with aberrant glycosylation. The proposed research program would develop novel molecular structures to investigate the molecular recognition of carbohydrates in normal and diseased biochemical systems, and develop novel chemoenzymatic methods for solution- and solid-phase glycoconjugate synthesis to facilitate theses endeavors. Specific research areas to be addressed include: (1) A program to determine the manner in which structural information is conveyed from proteins to their attached carbohydrat chains during O-linked glycoprotein biosynthesis. The general approach is to design and synthesize conformationally constrained variants of the N-acetylglucosaminyl serine glycoprotein linkage point, and substitute these for the parent linkage in oligopeptides. The net effect of these substitutions would be to fix the carbohydrate domain relative to the peptide in defined orientations. These glycopeptides would be evaluated as inhibitors or substrates of the Core 1 galactosyltransferase, and enzyme that catalyzes a glycosylation reaction in the early stages of mucin glycoprotein biosynthesis, and which is known to recognize both peptide and carbohydrate binding determinants within its substrates. The information gained from these investigations would provide a map of the transferase binding site, and would establish a foundation for development of therapeutic strategies based on selective inhibitors of protein glycosylation. (2) The development of novel chemical and enzymatic methods for the synthesis of complex glycoproteins and oligosaccharides to facilitate the study of their biochemical and cellular functions. In particular, a novel method for glycosylation with sialic acid an derivatives thereof, using sialyltransferases as synthetic catalysts, would be developed. Additionally, methods for the solid-phase synthesis of complex glycoproteins using a chemoselective ligation strategy would be developed. These would be suitable for combinatorial library generation, and could used i combination with conformational constraint to synthesize glycoproteins having strictly defined topologies. These molecules would open new avenues to investigate the functional roles of glycoconjugates in normal and disease-associated processes.
