Chen C H, Albers J J
Biochim Biophys Acta. 1985 Oct 2;836(3):279-85. doi: 10.1016/0005-2760(85)90131-6.
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 of 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.
将载脂蛋白A-IV、载脂蛋白E-2和载脂蛋白E-3分别掺入特定的磷脂酰胆碱/胆固醇脂质体中，以研究卵磷脂胆固醇酰基转移酶的激活情况。将这些脂质体获得的酶活性与含有纯化载脂蛋白A-I的脂质体的酶活性进行比较。载脂蛋白A-IV、载脂蛋白E-2和载脂蛋白E-3均能激活卵磷脂胆固醇酰基转移酶。以纯化酶和蛋黄磷脂酰胆碱作为酰基供体时，载脂蛋白A-IV浓度约为0.5 nmol、载脂蛋白E亚型浓度约为0.4 nmol时可获得最大激活效果。对于纯化酶的激活，载脂蛋白A-IV的效率约为载脂蛋白A-I的25%；载脂蛋白E-2为40%，载脂蛋白E-3为30%。以血浆作为酶源时也获得了类似的激活结果。对缺乏载脂蛋白A-I或仅含有微量载脂蛋白A-I的患者血浆进行分析，结果显示胆固醇酯化率和卵磷脂胆固醇酰基转移酶活性降低，且与该酶质量水平降低成比例。这些结果表明，载脂蛋白A-IV和载脂蛋白E可能作为该酶反应的生理辅因子。
