Mechanistic studies on shikimate pathway enzymes

莽草酸途径酶的机理研究

• 批准号: 138038-2006
• 负责人: Turnbull, Joanne
• 金额: $ 3.15万
• 依托单位: Concordia University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2006
• 资助国家: 加拿大
• 起止时间: 2006-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=337067
• 关键词: Mechanistic; studies; shikimate; pathway; enzymes

Enzymes can accelerate chemical reactions by more than a million-fold.  We are interested in understanding how amino acid residues within enzymes bring about this rate acceleration.  Some residues are involved in binding, others participate in the chemistry of the reaction, while other groups are involved in both. Our main focus is on enzymes involved in the biosynthesis of tyrosine. The enzymes under study, a mutase and a dehydrogenase, catalyze two consecutive reactions in this  pathway.  In some organisms, the reactions are catalyzed on separate polypeptides while in other bacteria, including E. coli the enzyme belongs to a special class called bifunctional proteins; two reactions are catalyzed on a single polypeptide.  We are interested in understanding how each of these enzyme-catalyzed reactions work separately, as well as delineating the relationship between the two activities.   In order to gain further information about one of the reactions in particular, we have recently solved the structure of a monofunctional dehydrogenase from a hyperthermophilic bacterium.  This structure is used to guide mutagenesis studies to probe the enzyme's mechanism of action and mode of regulation by tyrosine. Comparison of results with analogous studies on the bifunctional enzyme, for which there is no structure, help us gain insight into the interdependence of the two sites. The reactions catalyzed by these enzymes are specific to plants and microoganisms.  Knowledge of how specific enzymic residues bind to inhibitors could lead to the design of improved herbicides and antimicrobial agents.

酶可以将化学反应加速一百万倍以上。  我们有兴趣了解酶内的氨基酸残基如何带来这种速率加速。  一些残基参与结合，其他残基参与化学反应，而其他基团则参与两者。我们的主要关注点是参与酪氨酸生物合成的酶。所研究的酶（变位酶和脱氢酶）在此途径中催化两个连续反应。  在一些生物体中，这些反应是在单独的多肽上催化的，而在包括大肠杆菌在内的其他细菌中，酶属于称为双功能蛋白的特殊类别。单个多肽催化两个反应。  我们有兴趣了解每种酶催化反应如何单独发挥作用，以及描述两种活动之间的关系。   为了获得有关其中一个反应的更多信息，我们最近解析了来自超嗜热细菌的单功能脱氢酶的结构。  该结构用于指导诱变研究，以探究酶的作用机制和酪氨酸的调节模式。将结果与对没有结构的双功能酶的类似研究进行比较，有助于我们深入了解两个位点的相互依赖性。这些酶催化的反应是植物和微生物特有的。  了解特定酶残基如何与抑制剂结合可能有助于设计改进的除草剂和抗菌剂。