ENZYMIC REACTIONS OF MODEL PLASMA LIPOPROTEINS

卵磷脂：胆固醇酰基转移酶(LCAT)是主要的胆固醇 人血浆的酯化活性。它在城市改造中起着重要的作用 新生高密度脂蛋白(HDL)，富含游离 胆固醇，转化为成熟的高密度脂蛋白，其中大部分胆固醇在其 酯化形式。这一过程在胆固醇的运输中很重要。 从外周组织到肝脏，在那里一部分胆固醇 转化为胆盐。这种“反向胆固醇运输”是一种 动脉粥样硬化预防和消退的重要一步。这 该项目将侧重于两个重要领域；LCAT的监管和结构-- 函数关系。第一步将是在老鼠身上进行研究， 分离大鼠肝细胞和人肝癌细胞对饮食的影响 已知可影响血浆LCAT水平对LCAT mRNA、合成、 和分泌物。含n-3脂肪的甘油三酯对膳食的影响 改变人体血浆LCAT水平的酸对血浆LCAT水平 分泌物和周转率将与给予对照大鼠的比较 传统的食物或含有n-9脂肪酸的甘油三酯。人类的文化 将肝癌细胞用于直接比较n-3和n-6的效果 白蛋白复合体和模型重组高密度脂蛋白中的脂肪酸 被测脂肪酸位于磷脂酰胆碱的sn-2位。 游离胆固醇和胆固醇酯含量对人体健康的影响 模型高密度脂蛋白也将被确定。第二步是使用Site- 定向诱变和单抗明确识别 LCAT的一些功能区及其分子基础的确定 底物专一性，这在不同的哺乳动物中是不同的 物种。这些研究将描绘LCAT形成的机制 胆固醇酯，更好地局部化区域(S)负责结合 到脂蛋白表面，并揭示活性部位区域的差异 来自具有不同底物特异性的不同物种的LCAT。

Lecithin:cholesterol acyltransferase (LCAT) is the major cholesterol esterifying activity of human plasma. It is important in the remodeling of nascent high density lipoproteins (HDL), which are rich in free cholesterol, into mature HDL in which most of the cholesterol is in its esterified form. This process is important in the transport of cholesterol from peripheral tissues to the liver where a portion of the cholesterol if converted to bile salts. This "reverse cholesterol transport" is an important step in prevention and regression of atherosclerosis. This project will focus upon two important areas; LCAT regulation and structure- function relationships. The first step will be to investigate in rats, isolated rat hepatocytes, and human hepatoma cells the influence that diets which are known to affect plasma LCAT levels have on LCAT mRNA, synthesis, and secretion. The effects of dietary triglycerides containing n-3 fatty acids, which alter plasma LCAT levels in man, on plasma LCAT levels, LCAT secretion, and turnover will be compared with those of control rats given conventional chow or triglycerides with n-9 fatty acids. Cultures of human hepatoma cells will be used to directly compared the effects of n-3 and n-6 fatty acids in albumin complexes and in model reassembled HDL in which the test fatty acids are located at the sn-2 position of phosphatidylcholine. The effects of the free cholesterol and cholesteryl ester contents of the model HDL will also be determined. The second step will be to use site- directed mutagenesis and monoclonal antibodies to unambiguously identify some of the functional regions of LCAT and to determine the molecular basis of its substrate specificity, which is different in different mammalian species. These studies will delineate the mechanism by which LCAT forms cholesteryl esters, better localize the region(s) responsible for binding to lipoprotein surfaces, and reveal differences in the active site region of LCAT from different species that have different substrate specificities.