Shirai K, Ohsawa I, Ishikawa Y, Saito Y, Yoshida S
J Biol Chem. 1985 May 10;260(9):5225-7.
The possibility that some factor in serum changes the substrate specificity of purified human plasma carboxyl esterase, which hydrolyzes the short chain fatty acid ester, tributyrin, was investigated. The purified carboxyl esterase from human plasma hydrolyzed 48 mmol of tributyrin/mg of protein/h, monoolein at 1560 mumol of released fatty acids/mg of protein/h, diolein at 133 mumol of released fatty acids/mg of protein/h, and triolein at less than 10 mumol of released fatty acids/mg of protein/h. When human serum was applied to phenyl-Sepharose, a triolein hydrolysis-promoting factor (THPF) for purified carboxyl esterase was bound to the gel and was eluted with water. This partially purified human serum THPF enhanced carboxyl esterase-catalyzed triolein hydrolysis about 30-fold, diolein hydrolysis 2-fold, and monoolein hydrolysis 1.5-fold. Hydrolysis of triolein in very low density lipoproteins (d less than 1.006) and intermediate lipoproteins (1.006 less than d less than 1.019) by carboxyl esterase was also enhanced by addition of THPF. THPF activity was reduced by treatment of delipidation, but resistant to trypsin treatment or heating at 50 degrees C. These results indicated that serum carboxyl esterase can hydrolyze the long chain fatty acid ester, triolein, in the presence of triolein hydrolysis-promoting factor in serum.
研究了血清中的某些因素是否会改变纯化的人血浆羧酸酯酶的底物特异性，该酶可水解短链脂肪酸酯三丁酸甘油酯。从人血浆中纯化得到的羧酸酯酶每毫克蛋白质每小时可水解48 mmol三丁酸甘油酯，每毫克蛋白质每小时可水解1560 μmol单油酸甘油酯释放脂肪酸，每毫克蛋白质每小时可水解133 μmol二油酸甘油酯释放脂肪酸，每毫克蛋白质每小时水解三油酸甘油酯释放的脂肪酸少于10 μmol。将人血清应用于苯基琼脂糖时，纯化的羧酸酯酶的三油酸甘油酯水解促进因子（THPF）与凝胶结合，用水洗脱。这种部分纯化的人血清THPF可使羧酸酯酶催化的三油酸甘油酯水解提高约30倍，二油酸甘油酯水解提高2倍，单油酸甘油酯水解提高1.5倍。添加THPF也可增强羧酸酯酶对极低密度脂蛋白（d小于1.006）和中间密度脂蛋白（1.006小于d小于1.019）中三油酸甘油酯的水解。脱脂处理会降低THPF活性，但它对胰蛋白酶处理或50℃加热具有抗性。这些结果表明，在血清中三油酸甘油酯水解促进因子存在的情况下，血清羧酸酯酶可以水解长链脂肪酸酯三油酸甘油酯。
