Rojas C, Olivecrona T, Bengtsson-Olivecrona G
Department of Medical Biochemistry and Biophysics, University of Umeå, Sweden.
Eur J Biochem. 1991 Apr 23;197(2):315-21. doi: 10.1111/j.1432-1033.1991.tb15913.x.
We have compared the action of lipoprotein lipase on liposomes of egg yolk phosphatidylcholine containing less than saturating amounts of trioleoylglycerol (less than 3%) and emulsion droplets of the same lipids. The amounts of the two types of lipid particles (expressed in terms of phosphatidylcholine) needed to reach substrate saturation of the enzyme were similar, indicating similar binding of the lipase to these two lipid/water interfaces. With liposomes, as opposed to emulsion droplets, albumin was not necessary for continued hydrolysis of triacylglycerols, presumably because product fatty acids could be accommodated in the phospholipid bilayer. The maximal rate of trioleoylglycerol hydrolysis was more than 10-fold higher, and the ratio of trioleoylglycerol/phosphatidylcholine hydrolysis was more than 50-fold higher with the emulsion droplets. Qualitatively similar results were obtained with hepatic lipase, and a lipase from Pseudomonas fluorescence. The data suggest that the lipases remained at the interface for several catalytic cycles, and that a continued supply of substrate molecules to the active site favored triacylglycerol entry from the core of the lipid particle, rather than sliding in from the side through lateral diffusion in the surface layer.
我们比较了脂蛋白脂肪酶对含低于饱和量三油酰甘油（低于3%）的蛋黄磷脂酰胆碱脂质体以及相同脂质乳剂液滴的作用。达到该酶底物饱和所需的两种类型脂质颗粒的量（以磷脂酰胆碱表示）相似，这表明脂肪酶与这两个脂质/水界面的结合相似。与乳剂液滴不同，对于脂质体，三酰甘油的持续水解不需要白蛋白，推测这是因为产物脂肪酸可以容纳在磷脂双分子层中。三油酰甘油水解的最大速率高出10倍以上，乳剂液滴的三油酰甘油/磷脂酰胆碱水解比率高出50倍以上。用肝脂肪酶和荧光假单胞菌脂肪酶也获得了定性相似的结果。数据表明，脂肪酶在界面处停留进行了几个催化循环，并且向活性位点持续供应底物分子有利于三酰甘油从脂质颗粒核心进入，而不是通过表层的横向扩散从侧面滑入。
