MacPhee C E, Chan R Y, Sawyer W H, Stafford W F, Howlett G J
Russell Grimwade School of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia.
J Lipid Res. 1997 Aug;38(8):1649-59.
The central function of lipoprotein lipase (LpL) is to hydrolyze triacylglycerols in chylomicrons and very low density lipoproteins. We have examined the binding of purified milk lipoprotein lipase to homogeneous synthetic lipid emulsions. Emulsions composed of either naturally occurring ester-linked lipids or the non-hydrolyzable ether analogues were prepared by sonication and pressure extrusion, and fractionated by sucrose density gradient centrifugation. Flotation analysis using the analytical ultracentrifuge indicated that the individual fractions were relatively homogeneous with respect to size with flotation coefficients and molecular weights for the separated fractions ranging from 100 to 1100 S and 5.2 x 10(7) to 6.0 x 10(8), respectively. Purified milk lipoprotein lipase bound with high affinity and in a saturable manner to emulsions prepared from the non-hydrolyzable ether-linked lipid analogues of 1-oleoyl, 2-palmitoyl phosphatidylcholine and triolein. At low concentrations of LpL, the enzyme caused aggregation of the emulsion particles by interparticle cross-linking. At higher LpL concentrations, the flotation coefficient of the emulsions decreased significantly with a concomitant increase in particle density. At saturation, the number of LpL monomers bound to lipid particles of radii 67, 75, and 79 nm was 1315, 1449, and 1466, respectively. The results demonstrate close packing of LpL on the lipid surface and are consistent with there being little disruption to the overall structure of the emulsion particle.
脂蛋白脂肪酶（LpL）的核心功能是水解乳糜微粒和极低密度脂蛋白中的三酰甘油。我们研究了纯化的乳脂蛋白脂肪酶与均匀合成脂质乳剂的结合情况。通过超声处理和压力挤压制备了由天然存在的酯连接脂质或不可水解的醚类似物组成的乳剂，并通过蔗糖密度梯度离心进行分级分离。使用分析超速离心机进行的浮选分析表明，各个级分在大小方面相对均匀，分离级分的浮选系数和分子量分别为100至1100 S和5.2×10⁷至6.0×10⁸。纯化的乳脂蛋白脂肪酶以高亲和力且以饱和方式与由1-油酰基、2-棕榈酰磷脂酰胆碱和三油精的不可水解醚连接脂质类似物制备的乳剂结合。在低浓度的LpL下，该酶通过颗粒间交联导致乳剂颗粒聚集。在较高的LpL浓度下，乳剂的浮选系数显著降低，同时颗粒密度增加。在饱和时，与半径为67、75和79 nm的脂质颗粒结合的LpL单体数量分别为1315、1449和1466。结果表明LpL在脂质表面紧密堆积，并且与乳剂颗粒的整体结构几乎没有破坏一致。
