Haberbosch W, Poli A, Baggio G, Fellin R, Gnasso A, Augustin J
Biochim Biophys Acta. 1984 Mar 27;793(1):49-60. doi: 10.1016/0005-2760(84)90052-3.
Kinetic studies were performed incubating lipoprotein lipase and hepatic triacylglycerol lipase from human postheparin plasma with triacylglycerol-rich lipoproteins from two patients with apolipoprotein C-II deficiency. These lipoproteins differed in their lipid and apolipoprotein composition from normal very-low-density lipoproteins and chylomicrons. The addition of isolated apolipoprotein C-II and normal or apolipoprotein C-II-deficient high-density lipoproteins caused an increase of Vmax and a decrease of the Km for lipoprotein lipase-induced hydrolysis. Hepatic triacylglycerol lipase activity was not influenced by the presence of apolipoprotein C-II in the incubation medium, but was inhibited by increasing amounts of high-density lipoproteins. Binding studies were performed in order to analyze the interactions between lipolytic enzymes, apolipoprotein C-II, and triacylglycerol-rich lipoproteins. Apolipoprotein C-II was, as expected, rapidly taken up by apolipoprotein C-II-deficient very-low-density lipoproteins and chylomicrons when they were incubated with normal high-density lipoproteins or with the purified apolipoprotein. This uptake was inhibited by the addition of increasing amounts of lipoprotein lipase in conditions in which no lipolysis could occur. Binding of lipoprotein lipase to apolipoprotein C-II-deficient very-low-density lipoproteins or chylomicrons was not affected by the addition of apolipoprotein C-II when an excess of triacylglycerol-rich lipoprotein was present. The stability of lipoprotein lipase was also studied. Apolipoprotein C-II and high-density lipoproteins were unable to prolong the half-life of the enzyme activity, while triacylglycerol-rich particles effectively stabilized lipoprotein lipase. We conclude that binding of lipoprotein lipase to the substrate surface is not affected by apolipoprotein C-II. It is more likely that the peptide catalyzes the conversion of lipoprotein lipase from a less to a more active form.
进行了动力学研究，将人肝素后血浆中的脂蛋白脂肪酶和肝甘油三酯脂肪酶与两名载脂蛋白C-II缺乏症患者的富含甘油三酯的脂蛋白一起孵育。这些脂蛋白在脂质和载脂蛋白组成上与正常极低密度脂蛋白和乳糜微粒不同。添加分离的载脂蛋白C-II以及正常或载脂蛋白C-II缺乏的高密度脂蛋白会导致脂蛋白脂肪酶诱导的水解反应的Vmax增加，Km降低。肝甘油三酯脂肪酶活性不受孵育介质中载脂蛋白C-II存在的影响，但会受到高密度脂蛋白量增加的抑制。进行结合研究以分析脂解酶、载脂蛋白C-II和富含甘油三酯的脂蛋白之间的相互作用。正如预期的那样，当载脂蛋白C-II缺乏的极低密度脂蛋白和乳糜微粒与正常高密度脂蛋白或纯化的载脂蛋白一起孵育时，载脂蛋白C-II会迅速被摄取。在不会发生脂解的条件下，添加越来越多的脂蛋白脂肪酶会抑制这种摄取。当存在过量的富含甘油三酯的脂蛋白时，载脂蛋白C-II的添加不会影响脂蛋白脂肪酶与载脂蛋白C-II缺乏的极低密度脂蛋白或乳糜微粒的结合。还研究了脂蛋白脂肪酶的稳定性。载脂蛋白C-II和高密度脂蛋白无法延长酶活性的半衰期，而富含甘油三酯的颗粒可有效稳定脂蛋白脂肪酶。我们得出结论，脂蛋白脂肪酶与底物表面的结合不受载脂蛋白C-II的影响。更有可能的是，该肽催化脂蛋白脂肪酶从活性较低的形式转变为活性较高的形式。
