STRUCTURE/FUNCTION ANALYSIS OF ENZYMES

描述：高分辨率x射线结晶学研究 通过详细的动力学分析，已经对 尊重酶的结构和功能的关系。这样做的目的是 应用是在详细的分子水平上理解催化剂 四种酶系统的作用机制：假单胞菌磷酸三酯酶 它能分解某些杀虫剂和神经毒剂， 4-氯苯甲酰辅酶A脱卤酶和4-羟基苯甲酰辅酶A硫代酯酶 假单胞菌属参与该途径的CBS-3菌株 将4-氯苯甲酸酯转化为4-羟基苯甲酸酯和氨基甲酰磷酸酯 合成酶，产生高能的中间产物氨基甲酰磷酸。 这些酶的所有催化机制都被认为是 通过亲核攻击。这些酶被选为研究对象 由于它们有趣的生化特征。磷酸三酯酶 利用双核金属中心进行活性，而脱卤酶 催化亲核芳香族取代反应。反应机理的研究 硫代酯酶很可能通过亲核攻击进行，但 蛋白质的氨基酸序列表明，它与其他 到目前为止研究过的硫代酯酶。在氨基甲酰磷酸酯的情况下 合成酶，反应机制通过三种亲核攻击进行。 导致两个活性中间体，羧基磷酸盐和氨基甲酸酯。为 这些蛋白质，结合了定点突变实验和 将使用X射线晶体分析，以便更充分地 描述他们的三维架构、活动站点几何结构、 催化机理和底物特性。

DESCRIPTION: High resolution x-ray crystallographic studies, in combination with detailed kinetic analyses, have yielded a wealth of understanding with respect to enzyme structure and function relationships. The goal of this application is to understand, on a detailed molecular level, the catalytic mechanisms of four enzymatic systems: phosphotriesterase from Pseudomonas diminuta which hydrolyzes certain pesticides and nerve agents, 4-chlorobenzoyl CoA dehalogenase and 4-hydroxybenzoyl CoA thioesterase from Pseudomonas sp. strain CBS-3 which are involved in the pathway that converts 4-chlorobenzoate to 4-hydroxybenzoate, and carbamoyl phosphate synthetase which produces the high energy intermediate carbamoyl phosphate. All of the catalytic mechanisms for these enzymes are believed to proceed through nucleophilic attacks. These enzymes were chosen for investigation due to their interesting biochemical features. The phosphotriesterase utilizes a binuclear metal center for activity while the dehalogenase catalyzes nucleophilic aromatic substitutions. The reaction mechanism of the thioesterase most likely proceeds through a nucleophilic attack but the amino acid sequence of the protein suggests that it is not similar to other thioesterases studied thus far. In the case of carbamoyl phosphate synthetase, the reaction mechanism proceeds via three nucleophilic attacks leading to two reactive intermediates, carboxyphosphate and carbamate. For these proteins, a combination of site-directed mutagenesis experiments and x-ray crystallographic analyses will be employed in order to more fully characterize their three-dimensional architectures, active site geometries, catalytic mechanisms, and substrate specificities.