Catalysis by Prostaglandin Endoperoxide H Synthases

描述（由申请人提供）：前列腺素内过氧化物酶-1和-2（PGHS-1和-2），也称为环加氧酶-1和-2（考克斯-1和考克斯-2），在前列腺素（PG）生物合成的关键步骤中催化花生四烯酸（AA）转化为前列腺素H2（PGH2）。PGHS是考克斯抑制剂的主要靶点，包括非特异性非甾体抗炎药（nsNSAID）和称为coxib的考克斯-2特异性抑制剂。考克斯抑制剂是美国最广泛使用的药物，然而，使用这些抑制剂具有显著的风险。每年约有20 000人死于这些药物的不良反应，其分子基础尚不清楚。 使用纯化的人PGHS，我们已经发现，PGHS活动通过一个不寻常的变构机制调制的所有常见的脂肪酸（FA），包括那些不是PGHS底物。FA可以刺激或抑制PGHS活性，其特异性效应依赖于PGHS亚型和FA。这种效应发生在生理FA浓度下，并在细胞和纯化的酶中观察到。通过FA调节PGHS的生物化学基础涉及包含PGHS同二聚体的单体之间的串扰。虽然单体具有相同的氨基酸序列，但构成PGHS同二聚体的两个单体的构象不同。一个单体结合脂肪酸和行为作为一个变构单体，而另一个作为催化单体。最后且重要的是，纯化的人PGHS对考克斯抑制剂的反应受FA调节，这再次取决于FA、抑制剂和PGHS同种型。对于不同的考克斯抑制剂，FA可以影响抑制剂与一种或两种单体的结合。 拟议研究的目标是确定PGHS及其对广泛使用的考克斯抑制剂的反应如何在分子、细胞和整个动物水平上受到FA的影响。我们的基本假设是，无论是在体内PG的生产和反应考克斯抑制剂显着调制的环境中的FA酶找到自己的FA音，而且这种FA环境是重要的影响FA组成的饮食。我们假设，每个人建立一个FA音作为饮食习惯的结果，在他们的遗传背景的背景下。我们推测，某些FA色调易感个体考克斯抑制剂的不良后果。我们预计，我们描述FA/考克斯抑制剂相互作用的研究将成为第一步，导致改变向不同饮食的人开出考克斯抑制剂的方式，并调整饮食以提供更安全的使用考克斯抑制剂。

DESCRIPTION (provided by applicant): Prostaglandin endoperoxide H synthases-1 and -2 (PGHS-1 and -2), also known as cyclooxygenases-1 and -2 (COX-1 and COX-2), catalyze the conversion of arachidonic acid (AA) to prostaglandin H2 (PGH2) in the committed step of prostaglandin (PG) biosynthesis. PGHSs are the primary targets of COX inhibitors, which include nonspecific nonsteroidal anti-inflammatory drugs (nsNSAIDs) and COX-2 specific inhibitors called coxibs. COX inhibitors are the most widely used pharmaceutical agents in the U.S. However, the use of these inhibitors carries significant risks. About 20,000 deaths annually are attributable to adverse effects of these drugs, the molecular basis for which is unknown. Using purified human PGHSs, we have discovered that PGHS activities are modulated through an unusual allosteric mechanism by all common fatty acids (FAs) including those that are not PGHS substrates. FAs can stimulate or inhibit PGHS activity with the specific effect being dependent on the PGHS isoform and the FA. The effects occur at physiologic FA concentrations and are observed in cells as well as with purified enzymes. The biochemical basis for the regulation of PGHSs by FAs involves cross-talk between monomers comprising PGHS homodimers. Although the monomers have identical amino acid sequences, the conformations of the two monomers comprising a PGHS homodimer differ. One monomer binds FAs and behaves as an allosteric monomer while the other acts as the catalytic monomer. Finally and importantly, responses of purified human PGHSs to COX inhibitors are modulated by FAs, again depending on the FA, the inhibitor and the PGHS isoform. With different COX inhibitors, FAs can influence binding of an inhibitor to one or to both monomers. The goals of the proposed research are to determine how PGHSs and their responses to widely used COX inhibitors are affected by FAs at the molecular, cellular and whole animal levels. Our underlying hypothesis is that both in vivo PG production and responses to COX inhibitors are significantly modulated by the milieu of FAs in which the enzymes find themselves-the FA tone--and that this FA environment is importantly influenced by the FA composition of the diet. We presume that every individual establishes a FA tone as a consequence of dietary habits in the context of their genetic background. We speculate that certain FA tones predispose susceptible individuals to adverse consequences of COX inhibitors. We expect that our studies delineating FA/COX inhibitor interactions will be a first step leading to changes in the way COX inhibitors are prescribed to people on different diets and to dietary adjustments to provide for the safer use of COX inhibitors.