Pinon J C, Bridoux A M, Laudat M H
J Lipid Res. 1980 May;21(4):406-14.
The enzyme lecithin:cholesterol acyl transferase has been measured both in total plasma and in the fraction of plasma from which very low and low density lipoproteins have been removed by ultracentrifugation. The correlation between the activity of the enzyme and the free cholesterol concentration was positive in whole plasma and negative in apoB-deficient plasma. On the other hand, the positive correlation between plasma triglycerides and cholesterol esterification was not changed by the removal of apoB-containing lipoproteins. Subjects with the highest levels of high density lipoprotein cholesterol were found to have the lowest enzyme activity, but this correlation was disclosed only in apoB-deficient plasma. This inverse relationship was abolished when the enzyme activity was measured in the absence of all lipoproteins with a density less than 1.125 g/ml. Cholesterol esterification, when determined after removal of lipoproteins with a density less than 1.063 g/ml, was negatively correlated with the in vivo plasma concentration of lipoproteins in the density range 1.063-1.125 g/ml. The same results were obtained in vitro by addition of increasing amounts of this class of high density lipoproteins either in total plasma or in the ultracentrifuged fractions of plasma. This provides further evidence that the lighter density class of high density lipoproteins inhibits the enzyme reaction under physiological conditions.
胆固醇酰基转移酶。在全血浆中，该酶活性与游离胆固醇浓度呈正相关，而在载脂蛋白B缺乏的血浆中呈负相关。另一方面，去除含载脂蛋白B的脂蛋白后，血浆甘油三酯与胆固醇酯化之间的正相关并未改变。发现高密度脂蛋白胆固醇水平最高的受试者酶活性最低，但这种相关性仅在载脂蛋白B缺乏的血浆中才显现出来。当在不存在所有密度小于1.125 g/ml的脂蛋白的情况下测量酶活性时，这种负相关关系消失。去除密度小于1.063 g/ml的脂蛋白后测定的胆固醇酯化与密度范围为1.063 - 1.125 g/ml的脂蛋白的体内血浆浓度呈负相关。通过在全血浆或血浆超速离心组分中添加越来越多此类高密度脂蛋白，在体外也获得了相同的结果。这进一步证明，在生理条件下，密度较轻的高密度脂蛋白类别会抑制酶反应。
