Glycosidases and Glycosyl Transferases

碳水化合物和含碳水化合物的糖蛋白是生命所必需的。催化这些分子的分解(糖苷酶)和合成(糖基转移酶)的酶在生物学中起着关键作用，在医学和生物技术中有许多实际应用。例如，纤维素和相关的木聚糖是地球上碳含量最丰富的形式。因此，裂解这些碳水化合物的糖苷酶在食品、纺织、造纸和燃料生产中具有巨大的“绿色化学”作用。相反，抑制糖苷酶和糖基转移酶作用的化合物可能有助于控制微生物感染、糖尿病、癌症和神经退化等疾病。因此，这些酶仍然是深入研究的主题，旨在了解和操纵它们构建或降解碳水化合物底物的机制。我们的研究计划涉及使用强大的核磁共振光谱技术作为“分子显微镜”来：(I)测量糖苷酶在糖类结合和切割反应路径上发生的依赖于pH的静电性质的变化；(Ii)研究分子运动在底物结合和随后的糖基转移酶合成碳水化合物中的作用；(Iii)并确定糖蛋白与碳水化合物化学连接时性质的变化。从这些模式酶的共同/不同特征中吸取的经验教训将有助于我们理解自然界中发现的众多糖苷酶和糖基转移酶作用于碳水化合物的基本机制。根据医学应用的需要，这些信息可能有助于设计专门抑制这些酶的化合物。同时，这些研究将为设计糖苷酶提供必要的背景，这些糖苷酶的活性依赖于pH，适用于生物技术，包括纸浆和造纸业在高pH下的生物漂白。这项研究还为学生和博士后研究员提供了令人兴奋的培训，为他们未来在加拿大生物技术、医学和学术界的职业生涯做好准备。

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.