Nakaya K, Ushiwata A, Nakamura Y
Biochim Biophys Acta. 1976 Jul 19;439(1):116-24. doi: 10.1016/0005-2795(76)90167-7.
Tryptic activity was competitively inhibited by cationic detergents which contain a cetyl group or longer hydrocarbon chains. Since the cetyl group is much longer than the side chains of lysine or arginine residues of substrates for trypsin, the nature of inhibition by cetyldimethylbenzylammonium chloride was examined using Na-benzoyl-L-arginine-p-nitroanilide as substrate and compared to that by butylamine. The inhibition by cetyldimethylbenzylammonium chloride occurred instantaneously and was completely reversible. The inhibitory effect of cetyldimethylbenzylammonium chloride was strongly dependent on both pH and salt concentration, contrasting with inhibition by butylamine which was relatively indifferent to these changes. The Ki value of cetyldimethylbenzylammonium chloride at pH 7.5 and 25 degrees C was calculated to be 2.0 +/- 0.3 mM, which is equal to that of butylamine within experimental errors. The standard entropy change of binding of cetyldimethylbenzylammonium chloride (44 +/- 2 cal/mol/degree) was much larger than for butylamine, indicating the formation of an efficient hydrophobic bond between the cetyl group and the enzyme.
含有十六烷基或更长烃链的阳离子洗涤剂可竞争性抑制胰蛋白酶活性。由于十六烷基比胰蛋白酶底物中赖氨酸或精氨酸残基的侧链长得多，因此以苯甲酰-L-精氨酸对硝基苯胺钠为底物，研究了十六烷基二甲基苄基氯化铵的抑制性质，并与丁胺的抑制性质进行了比较。十六烷基二甲基苄基氯化铵的抑制作用瞬间发生且完全可逆。十六烷基二甲基苄基氯化铵的抑制作用强烈依赖于pH值和盐浓度，这与丁胺的抑制作用形成对比，丁胺对这些变化相对不敏感。在pH 7.5和25℃下，十六烷基二甲基苄基氯化铵的Ki值经计算为2.0±0.3 mM，在实验误差范围内与丁胺的Ki值相等。十六烷基二甲基苄基氯化铵结合的标准熵变（44±2 cal/mol/℃）比丁胺的大得多，表明十六烷基与酶之间形成了有效的疏水键。
