STRUCTURE AND INTERFACIAL FUNCTION OF PLATELET ACTIVATING FACTOR ACETYLHYDROLASE

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。脂质代谢是一个主要的人类健康问题，人们非常关注与低密度脂蛋白和高密度脂蛋白（LDL， HDL）相关的脂质炎症和脂质稳态。许多与LDL和HDL颗粒相关的蛋白质在这些脂质途径中起关键作用。血浆形式的血小板活化因子乙酰水解酶（pPAFAH）通过降低信号分子血小板活化因子（PAF）的水平在LDL颗粒表面起作用，作为一种一般的抗炎清道夫，与过敏性休克、哮喘和过敏反应有关。pPAFAH是一种低密度脂蛋白相关蛋白，没有已知的同源物，是一个有价值的结构靶点。除了其降低PAF水平的作用外，它还与其他促炎剂的水解活性有关，如氧化LDL颗粒的脂质。对pPAFAH催化的生理反应的分子理解需要酶与其底物PAF和氧化磷脂相互作用的结构模型。我们将通过四个具体目标阐明pPAFAH的结构与界面酶功能之间的关系：(1)解决pPAFAH的高分辨率晶体结构。将探索洗涤剂和两亲分子的使用，以提供更高分辨率的结构，以及功能上更相关的结构。（ii） pPAFAH抑制剂将通过结构和动力学表征来探索和开发，以阐明其在体内的生理功能。（iii）结合结构与界面动力学研究，进一步阐明pPAFAH的生理作用。从抑制和结构研究的见解将有助于开发酶的原子分解机制。酶-配体复合物将进一步阐明酶的作用机制。（iv） pPAFAH与有机磷（OP）化合物的生理相关反应将被探索，包括ldl相关酶作为有机磷神经毒素的生物清除剂靶点的可能性。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Lipid metabolism is a major human health concern, with much attention focused on inflammation and lipid homeostatis of lipids linked to low and high density lipoprotein (LDL, HDL). Many proteins that are associated with LDL and HDL particles play a critical role in these lipid pathways. The plasma form of platelet activating factor acetylhydrolase (pPAFAH) functions on the surface of LDL particles by reducing levels of the signaling molecule platelet activating factor (PAF) as a general anti-inflammatory scavenger, and is linked to anaphylactic shock, asthma and allergic reactions. As a LDL-associated protein with no known homologues, pPAFAH is a worthy structural target. In addition to its role to reduce PAF levels, it has also been implicated in hydrolytic activities of other pro-inflammatory agents, such as oxidized lipids of LDL particles. A molecular understanding of the physiological reactions catalyzed by pPAFAH requires structural models of the enzyme interacting with its substrates PAF and oxidized phospholipids. We will elucidate the relationship between structure and interfacial enzyme function for pPAFAH via 4 specific aims: (i) The high-resolution crystal structure of pPAFAH will be solved. The use of detergents and amphiphilic molecules will be explored to provide higher resolution structures, as well as functionally more relevant structures. (ii) Inhibitors of pPAFAH will be explored and developed via structural and kinetic characterization to elucidate in vivo physiological functions. (iii) Combining structure with interfacial kinetic studies, we will further elucidate the physiological roles of pPAFAH. Insights from inhibition and structural studies will help develop an atomic resolution mechanism of the enzyme. Enzyme-ligand complexes will be pursued that further elucidate the enzyme mechanism. (iv) The physiologically relevant reaction of pPAFAH with organophosphate (OP) compounds will be explored, including the possible use of the LDL-associated enzyme as a bioscavenger target of OP neurotoxins.