ACTIVATION OF LECITHIN - CHOLESTEROL ACYLTRANSFERASE BY APOLIPOPROTEIN-E-2, APOLIPOPROTEIN-E-3, AND A-IV ISOLATED FROM HUMAN-PLASMA
ACTIVATION OF LECITHIN - CHOLESTEROL ACYLTRANSFERASE BY APOLIPOPROTEIN-E-2, APOLIPOPROTEIN-E-3, AND A-IV ISOLATED FROM HUMAN-PLASMA
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DOI：
10.1016/0005-2760(85)90131-6
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发表时间：
1985-01-01
期刊：
影响因子：
--
通讯作者：
ALBERS, JJ
中科院分区：
文献类型：
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作者：
CHEN, CH;ALBERS, JJ
将载脂蛋白A-IV、载脂蛋白E-2和载脂蛋白E-3分别掺入确定的磷脂酰胆碱/胆固醇脂质体中，用于研究卵磷脂：胆固醇酰基转移酶活化。用这些脂质体获得的酶活性与含有纯化的载脂蛋白A-I的脂质体进行比较。载脂蛋白A-IV、载脂蛋白E-2和载脂蛋白E-3均激活卵磷脂：胆固醇酰基转移酶。用纯化的酶和蛋黄磷脂酰胆碱作为酰基供体，在载脂蛋白A-IV约0.5 nmol和载脂蛋白E亚型0.4 nmol的浓度下获得最大活化。载脂蛋白A-IV激活纯化酶的效率约为载脂蛋白A-I的25%;载脂蛋白E-2的效率为40%，载脂蛋白E-3为30%。使用血浆作为酶源也获得了类似的激活结果。对无载脂蛋白A-I或仅含微量载脂蛋白A-I患者的血浆分析显示，胆固醇酯化率和卵磷脂：胆固醇酰基转移酶活性降低，与酶质量降低水平成正比。这些结果表明，载脂蛋白A-IV和载脂蛋白E可能作为酶反应的生理辅助因子。
Apolipoprotein A-IV, apolipoprotein E-2 and apolipoprotein E-3 were individually incorporated into defined phosphatidylcholine/cholesterol liposomes for study of lecithin:cholesterol acyltransferase activation. Enzyme activities obtained with these liposomes were compared with that from liposomes containing purified apolipoprotein A-I. Apolipoprotein A-IV, apolipoprotein E-2, and apolipoprotein E-3 all activated lecithin:cholesterol acyltransferase. With purified enzyme and with egg yolk phosphatidylcholine as the acyl donor, maximal activation was obtained at a concentration of approximately 0.5 nmol for apolipoprotein A-IV and 0.4 nmol for the apolipoprotein E isoforms. Apolipoprotein A-IV was approximately 25% as efficient as apolipoprotein A-I for the activation of purified enzyme; apolipoprotein E-2 was 40% as efficient, and apolipoprotein E-3, 30%. Similar activation results were obtained using plasma as the enzyme source. Analysis of the plasma of patients with absence of apolipoprotein A-I or with only trace amounts apolipoprotein A-I exhibited a reduced rate of cholesterol esterification and lecithin:cholesterol acyltransferase activity that was proportional to the reduced level of the enzyme''s mass. These results indicate that apolipoprotein A-IV and apolipoprotein E may serve as physiological cofactors for the enzyme reaction.