STRUCTURE/FUNCTION OF PROSTAGLANDIN H SYNTHASE 2

前列腺素H合酶（PGHS）的环氧合酶活性催化 在生物合成的第一个关键步骤， 一组有效的，生物活性的脂质，被认为在许多 病理生理过程，包括炎症、血管、胃 以及肾功能、生殖和肿瘤发生。两种PGHS亚型是 已知：PGHS-1被认为是组成型的，被认为是管家型的。 PGHS 2在许多相关细胞中可被细胞因子强烈诱导 在炎症和增殖过程中。除了PGHS的控制之外， 1和-2基因表达，细胞前列腺素合成也紧密 调节在环氧合酶催化水平，与不同的催化 两种PGHS同种型的对照。PGHS-2环氧合酶具有很大的 比PGHS-1环氧合酶更低的氢过氧化物活化剂需求。 产品反馈激活的这种差异提供了一个简单的 环加氧酶细胞差异控制的生化基础 催化作用细胞环氧合酶的催化作用也会受到脂肪酸的限制。 酸性底物利用率PGHS-1环氧合酶活性显示 在低花生四烯酸水平的合作行为，而PGHS-2 酶遵循简单的饱和动力学。本项目的总体目标 是了解PGHS异构体对催化的调节， 分子水平。动力学、光谱学和结构研究将在 用两种PGHS同种型和靶向突变蛋白进行， 实现以下具体目标：1）确定机制基础 对于PGHS-1和PGHS-2中不同的氢过氧化物活化剂要求， 并研究阿司匹林处理的PGHS-2的机制变化; 2） 确定控制氢过氧化物活化剂的结构元素 PGHS-1和-2中的要求，并研究 阿司匹林处理的PGHS-2; 2）确定控制 两种异构体中的氢过氧化物活化剂要求;和3） 评估脂肪酸和过氧化物之间的相互依赖性， 环氧合酶对两种PGHS同工型的催化控制。

The cyclooxygenase activity of prostaglandin H synthase (PGHS) catalyzes the first committed step in the biosynthesis of the prostaglandins, a group of potent, bioactive lipids believed important in many pathophysiological processes, including inflammation, vascular, gastric and renal function, reproduction, and tumorigenesis. Two PGHS isoforms are known: PGHS-1 is regarded as constitutive and is ascribed housekeeping function; PGHS 2 is strongly inducible by cytokines in many cells involved in inflammatory and proliferative processes. Besides the controls of PGHS- 1 and -2 gene expression, cellular prostaglandin synthesis is also tightly regulated at the cyclooxygenase catalytic level, with different catalytic controls for the two PGHS isoforms. PGHS-2 cyclooxygenase has a much lower hydroperoxide activator requirement than the PGHS-1 cyclooxygenase. This difference in feedback activation by the product provides a simple biochemical basis for differential cellular control of cyclooxygenase catalysis. Cellular cyclooxygenase catalysis also can be limited by fatty acid substrate availability. PGHS-1 cyclooxygenase activity exhibits cooperative behavior at low arachidonic acid levels, whereas the PGHS-2 enzyme follows simple saturable kinetics. The general goal of this project is to understand the regulation of catalysis by the PGHS isoforms at a molecular level. Kinetic, spectroscopic, and structural studies will be undertaken with the two PGHS isoforms and targeted mutant proteins to achieve the following specific aims: 1) Identify the mechanistic basis(es) for the different hydroperoxide activator requirements in PGHS-1 and -2, and investigate the mechanistic changes in aspirin-treated PGHS-2; 2) Identify the structural element(s) controlling the hydroperoxide activator requirements in PGHS-1 and -2, and investigate the mechanistic changes in aspirin-treated PGHS-2; 2) Identify the structural element(s) controlling the hydroperoxide activator requirements in the two isoforms; and 3) Evaluate the interdependence between fatty acid and peroxide in cyclooxygenase catalytic control for the two PGHS isoforms.