PAF ACETYLHYDROSE & CONTROL OF PEROXIDATIVE DAMAGE TO SPERM MEMBRANES

长期目标O？如果我们的研究是为了了解 精子膜脂质组成的生理相关性， 改变和扰乱它的因素。一个因素已经出现， 尤其是对精子的损害，是导致精子缺陷的主要原因 功能是脂质过氧化。 产生的机制 和脂质过氧化物的繁殖及其破坏作用， 有文件记载，但对限制损害的机制知之甚少， 开始过氧化反应。 最近的报告表明，膜 在氧化降解过程中裂解的磷脂提供了独特的 一种特殊磷脂酶A2，PAF乙酰水解酶底物 （PAF-A-H），它识别膜内受损的脂质， 选择性地水解它们，使正常的磷脂保持完整。 在过氧化降解时，醚连接的多不饱和的 哺乳动物精子特有的磷脂提供了 这种酶重要底物。 我们确定 牛精浆中PAF-AH比活性约为0.001。 40-到 50-比任何其他生物液体的报告高出一倍 并且精浆选择性地水解 氧化片段化磷脂。 我们认为这种酶 在限制精子的过氧化损伤方面起着重要作用， 以及具有PAF样的生物活性脂质的不期望的释放 精子在女性生殖道运输过程中的活动。 本研究的具体目标是：（1）表征 精子过氧化降解产生的分子种类 膜及其对精子活力的影响;（2）测定 氧化损伤精子PL对PAF-AH的底物特异性;（3） 精浆中PAF-AH的产生特点及其与精浆中PAF-AH的关系 与精子功能和生育力的关系;（4）纯化PAF-AH 以进一步表征其对精子的影响 膜的结构和功能

The long-term objective O?'f our research is to understand the physiological relevance of sperm membrane lipid composition and factors that modify and perturb it. A factor that has emerged as especially damaging to sperm and a leading cause of defective sperm function is lipid peroxidation. Mechanisms leading to the generation and propagation of lipid peroxides and their damaging effects are documented but less is known about mechanisms to limit the damage once peroxidation has begun. Recent reports demonstrate that membrane phospholipids cleaved during oxidative degradation provide a unique substrate for a special phospholipase A2, PAF acetylhdyrolase (PAF-A-H), which recognizes damaged lipids within the membrane and selectively hydrolyses them, leaving normal phospholipids intact. Upon peroxidative degradation, the ether-linked, polyunsaturated phosphohpids characteristic of mammalian sperm provide the most important substrate for this enzyme. We have determined that the specific activity of PAF-AH in bovine seminal plasma is ca. 40- to 50-fold higher than that reported for any other biological fluid andthat seminal plasma selectively hydrolyses structural analogues of oxidatively fragmented pbospholipids. We propose that this enzyme plays an important role in limiting peroxidative damage to sperm, as well as the undesirable release of bioactive lipids with PAF-like activity during sperm transport in the female reproductive tract. Specific aims of this research project are to:(1) Characterize the molecular species resulting from peroxidative degradation of sperm membrane and their effect on sperm viability; (2) Determine the substrate specificity of oxidatively damaged sperm PLs for PAF-AH; (3) Characterize the production of PAF-AH in seminal plasma andits relationship to sperm function and fertility; and (4) Purify PAF-AH from seminal plasma to characterize further its effects on sperm membrane structure and function.