Glycosidases and Glycosyl Transferases

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Carbohydrates and carbohydrate-containing glycoproteins are essential to life. The enzymes that catalyze the breakdown (glycosidases) and synthesis (glycosyl transferases) of these molecules play critical roles in biology and have many practical applications in medicine and biotechnology. For example, cellulose and related xylan are the most abundant forms of carbon on earth. Accordingly, the glycosidases that cleave these carbohydrates have enormous "green chemistry" roles in food, textile, paper, and fuel production. Conversely, compounds that inhibit the action of glycosidases and glycosyl transferases may help control diseases such as microbial infections, diabetes, cancer, and neurodegeneration. Therefore, these enzymes remain the subject of intensive research aimed towards understanding and manipulating the mechanisms by which they build or degrade their carbohydrate substrates. Our research program involves using the powerful technique of NMR spectroscopy as a "molecular microscope" to: (i) measure changes in the pH-dependent electrostatic properties of glycosidases occurring along their reaction pathways of carbohydrate binding and cleavage; (ii) investigate the roles of molecular motions in substrate binding and subsequent carbohydrate synthesis by glycosyl transferases; (iii) and determine how the properties of glycoproteins change when chemically linked to carbohydrates. The lessons learned from the common/distinct features of these model enzymes will help us understand the fundamental mechanisms by which the numerous glycosidases and glycosyl transferases found in nature act on carbohydrates. This information may aid in the design of compounds to specifically inhibit these enzymes, as required for medical applications. In parallel, these studies will provide the needed background to engineer glycosidases with pH-dependent activities tailored for use in biotechnology, including bio-bleaching at high pH in the pulp and paper industry. The research also provides exciting training for students and postdoctoral fellows, preparing them for future careers in Canadian biotechnology, medicine, and academia.