Tsujita T, Nakagawa A, Shirai K, Saito Y, Okuda H
J Biol Chem. 1984 Sep 25;259(18):11215-20.
Hepatic triglyceride lipase was obtained from post-heparin plasma of rats in an electrophoretically homogeneous form. The enzyme had an isoelectric point at pH 4.9 and molecular weight of 65,000. The relation between the "lipase" and "esterase" activities of the enzyme was studied using emulsified triolein and water-soluble methyl butyrate (80 mM) as substrates. The same enzyme protein catalyzed the hydrolyses of both emulsified triolein and water-soluble methyl butyrate. The relation of activity to the methyl butyrate concentration differed from those for pancreatic lipase and liver esterase. During purification, the ratio of methyl butyrate to triolein-hydrolyzing activity of the enzyme increased. On digestion of the enzyme with trypsin, the "lipase" activity was retained. However, the trypsin-treated enzyme was adsorbed to a heparin-Sepharose column and eluted with 0.75 M NaCl, like the untreated enzyme. These results suggest that rat hepatic triglyceride lipase contains a so-called "hydrophobic recognition site" that is destroyed by trypsin treatment and is distinct from the heparin-binding and catalytic sites.
肝甘油三酯脂肪酶以电泳纯的形式从大鼠肝素后血浆中获得。该酶的等电点为pH 4.9，分子量为65,000。以乳化三油酸甘油酯和水溶性丁酸甲酯（80 mM）为底物，研究了该酶的“脂肪酶”和“酯酶”活性之间的关系。同一酶蛋白催化乳化三油酸甘油酯和水溶性丁酸甲酯的水解。其活性与丁酸甲酯浓度的关系不同于胰脂肪酶和肝酯酶。在纯化过程中，该酶水解丁酸甲酯与水解三油酸甘油酯的活性之比增加。用胰蛋白酶消化该酶后，“脂肪酶”活性得以保留。然而，经胰蛋白酶处理的酶与未处理的酶一样，被吸附到肝素-琼脂糖柱上，并用0.75 M NaCl洗脱。这些结果表明，大鼠肝甘油三酯脂肪酶含有一个所谓的“疏水识别位点”，该位点在胰蛋白酶处理后被破坏，且与肝素结合位点和催化位点不同。
