Interactions and Reactions of Carbohydrates and Proteins

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The enzymes involved in the hydrolysis of glycosidic bonds (glycosidases) play a range of important biological roles, ranging from the degradation of polysaccharides such as starch and cellulose in digestive processes to the exquisitely selective 'trimming' of glycoproteins required for individual cells to interact with each other and with their environment. A detailed understanding of how these highly efficient catalysts (they accelerate reactions some billion-billion fold) work is valuable, not only in understanding catalysis itself, and engineering these enzymes to carry out novel reactions, but also in the design and synthesis of specific inhibitors to control cellular processes, thus possibly as therapeutics. This proposal comprises three parts. In the first part we propose mechanistic studies to unravel details of a novel mechanism that we have been studying from an enzyme from a pathogenic bacterium: this could lead to inhibitors to control infection. We also propose detailed mechanistic studies to understand how enzymes catalyze reactions so effectively and how they control their pH optima. In the second part, triggered by recent findings of how Mother Nature makes sugar mimetics, we propose to explore whether other classes of enzyme can carry out similar reactions. Finally we propose a methodology to "retrain" glycosyltransferases, enzymes that make useful sugar derivatives, to do so using inexpensive starting materials. To do this we shall harness the tools of genetics, microbiology, cell biology and analytical and organic chemistry in a process known as "directed evolution". This could lead to improved manufacturing strategies for sugar-based therapeutics and other products.