Carrero P, Gómez-Coronado D, Olivecrona G, Lasunción M A
Unidad de Dislipemias, Hospital Ramón y Cajal, Madrid, Spain.
Biochim Biophys Acta. 1996 Jan 19;1299(2):198-206. doi: 10.1016/0005-2760(95)00209-x.
The binding of lipoprotein lipase (LPL) to different lipoproteins and to a lipid emulsion was studied. After incubating the same amount of 125I-labelled LPL with VLDL, LDL or a lipid emulsion containing no apolipoproteins, we separated the free enzyme from the lipoprotein-bound LPL by gel filtration and by lipoprotein precipitation with phosphotungstic acid. By the former method we observed that all these types of lipid particles bound LPL indicating that the lipid moiety accounts for the LPL-lipoprotein interaction. This binding of LPL to lipoproteins was disrupted by high salt concentrations. When balanced by the apolipoprotein B content, it was observed that a significantly higher amount of 125I-labelled LPL co-eluted with VLDL than with LDL in gel permeation. The Kd values for binding of LPL to lipoproteins were estimated by use of lipoprotein precipitation. The obtained Kd values, both in the absence and in the presence of human lipoprotein deficient serum, were lower for VLDL than for LDL indicating a higher affinity of LPL for VLDL than for LDL. We finally compared binding capacity of LPL to VLDL subfractions with different apo E content. For this, we used apo E-poor (VLDL-B) and apo E-rich (VLDL-D) subfractions separated by heparin-Sepharose chromatography. We found that 125I-labelled LPL co-eluted to a similar extent with both subfractions on gel filtration, and the estimated Kd values from lipoprotein precipitation were not statistically different. Taken together, our results indicate that the lipid moiety, probably the phospholipids, accounts for the LPL-lipoprotein interaction; differences in size, the presence of C apolipoproteins or the conformation of apo B may be responsible for the higher affinity of LPL for VLDL than for LDL herein observed.
研究了脂蛋白脂肪酶（LPL）与不同脂蛋白以及脂质乳剂的结合情况。将等量的125I标记的LPL与极低密度脂蛋白（VLDL）、低密度脂蛋白（LDL）或不含载脂蛋白的脂质乳剂孵育后，我们通过凝胶过滤以及用磷钨酸沉淀脂蛋白的方法，将游离酶与结合在脂蛋白上的LPL分离。通过前一种方法，我们观察到所有这些类型的脂质颗粒都能结合LPL，这表明脂质部分参与了LPL与脂蛋白的相互作用。高盐浓度会破坏LPL与脂蛋白的这种结合。当以载脂蛋白B含量进行平衡时，在凝胶渗透实验中观察到，与LDL相比，有显著更多的125I标记的LPL与VLDL共洗脱。通过脂蛋白沉淀法估算LPL与脂蛋白结合的解离常数（Kd）值。在不存在和存在人脂蛋白缺乏血清的情况下，所获得的VLDL的Kd值均低于LDL，这表明LPL对VLDL的亲和力高于对LDL的亲和力。我们最后比较了LPL对不同载脂蛋白E含量的VLDL亚组分的结合能力。为此，我们使用了通过肝素 - 琼脂糖层析分离得到的载脂蛋白E含量低的（VLDL - B）和载脂蛋白E含量高的（VLDL - D）亚组分。我们发现，在凝胶过滤实验中，125I标记的LPL与这两种亚组分的共洗脱程度相似，并且通过脂蛋白沉淀法估算的Kd值在统计学上没有差异。综上所述，我们的结果表明，脂质部分，可能是磷脂，参与了LPL与脂蛋白的相互作用；大小差异、C类载脂蛋白的存在或载脂蛋白B的构象可能是本文观察到的LPL对VLDL的亲和力高于对LDL的亲和力的原因。
