Twu J S, Nilsson-Ehle P, Schotz M C
Biochemistry. 1976 May 4;15(9):1904-9. doi: 10.1021/bi00654a017.
The relationship between triacylglycerol and monoacylglycerol hydrolyzing activities of purified rat heart lipoprotein lipase was studied using emulsified trioleoylglycerol and micellar or albumin-bound monooleoylglycerol as substrates. The maximal reaction rates obtained with the two substrates were similar (650 and 550 nmol of fatty acid released per min per mg of protein, respectively). Addition of apolipoprotein C-II or serum increased the maximal reaction rate for the trioleolyglycerol hydrolyzing activity about four-fold, but had no effect on the monooleolyglycerol hydrolyzing activity. Hydolysis of the two substrates apparently takes place at the same active site of the enzyme since (1) mutual competitive inhibition between the substrates could be demonstrated; (2) the rate of inactivation of enzymatic activity with the two substrates in 1.2 M NaCl was the same; (3) similar losses of hydrolytic activity with tri- and monooleoylglycerol were observed in the presence of low concentrations of n-butyl (p-nitrophenyl) carbamide; (4) inhibition of both hydrolytic activities by this compound could be prevented by prior exposure of lipoprotein lipase to either substrate.
以乳化的三油酰甘油以及胶束态或与白蛋白结合的单油酰甘油为底物，研究了纯化的大鼠心脏脂蛋白脂肪酶的三酰甘油水解活性与单酰甘油水解活性之间的关系。用这两种底物获得的最大反应速率相似（分别为每分钟每毫克蛋白质释放650和550 nmol脂肪酸）。添加载脂蛋白C-II或血清可使三油酰甘油水解活性的最大反应速率提高约四倍，但对单油酰甘油水解活性没有影响。两种底物的水解显然发生在酶的同一活性位点，因为：（1）可以证明底物之间存在相互竞争性抑制；（2）在1.2 M NaCl中，两种底物使酶活性失活的速率相同；（3）在低浓度的正丁基（对硝基苯基）脲存在下，观察到三油酰甘油和单油酰甘油的水解活性有相似的损失；（4）该化合物对两种水解活性的抑制作用可通过使脂蛋白脂肪酶预先接触任何一种底物来防止。
