Probing the synergy between general acid and nucleophilic catalysis in highly efficient glycoside hydrolysis

• Applicant: Dr. Miriam P. Kötzler
• Subject Area: Biochemistry ; Biological and Biomimetic Chemistry ; Organic Molecular Chemistry - Synthesis and Characterisation ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2015 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 269277589

Polysaccharides are a valuable and renewable resource for fine chemicals. Effective depolymerization of these highly stable polymers is of high interest for industrial applications. Hence, understanding routes for catalyzed hydrolysis of the glycosidic bond is of fundamental importance to the design of tailored cost-efficient, stable and specific catalysts. Furthermore, the design of specific glycosidase inhibitors as therapeutic drugs demands that our understanding of their catalytic strategies is precise and correct. Enzymes are the world's most efficient catalysts and glycosidases achieve rate enhancements of up to 10 to 17 fold compared to the uncatalyzed reaction. Two catalytic strategies, i.e., general acid and nucleophilic catalysis are employed by most glycosidases. A significant part of enzymatic proficiency is attributed to synchronization of these two catalytic strategies within the reaction mechanism. Although widely suggested, this hypothesis has been remarkably difficult to prove in model systems or in enzymes themselves. This project aims to probe this synergy experimentally for the first time using a model glycosidase. Therefore, unnatural variants of the enzyme will be prepared by means of synthetic methods. In these synthetic variants, either of the two catalytic strategies is successively attenuated. By measuring the effect of this attenuation on catalytic efficiency, the dependence of one catalytic strategy on the other will be revealed. These kinetic experiments will be combined with physical methods to determine structural features of the altered catalytic pathways. Finally, these data will complement computational simulations of the catalyzed reaction, thereby offering general insights into how glycosides can be hydrolyzed with high efficiency.

• DFG Programme: Research Fellowships
• International Connection: Canada
• Host: Professor Dr. Stephen G. Withers