Schroeder L L, Pappas P W, Means G E
J Parasitol. 1981 Jun;67(3):378-85.
In the presence of intact Hymenolepis diminuta, trypsin was inactivated; intact worms had no apparent effect on subtilisin, pepsin, or papain. Inactivation of trypsin was demonstrable using azoalbumin as a substrate, but the inactivated enzyme retained full catalytic activity against benzoyl-DL-arginine-p-nitroanilide, p-tosyl-L-arginine methyl ester (low molecular weight synthetic trypsin substrates) and p-nitro-p-guanidinobenzoate (an active site titrant). Inactivation was not reversible under conditions of heating, freezing and thawing, or prolonged dialysis of the enzyme. Analyses of inactivated 3H-trypsin by cationic and SDS-polyacrylamide gel electrophoresis, and gel chromatography failed to indicate the presence of a high molecular weight trypsin inhibitor associated with the inactivated enzyme; no low molecular weight, dissociable inhibitor was demonstrable following thermal denaturation of the inactivated enzyme. Analyses of trypsin after incubation in the presence of pulse-labeled worms also failed to demonstrate the presence of any inhibitor of worm origin associated with the inactivated enzyme. The data suggest that inactivation is the result of a small structural or conformational change in the enzyme molecule, a change which partially (rather than totally) inactivates the enzyme towards protein substrates.
在微小膜壳绦虫完整存在的情况下，胰蛋白酶会失活；完整的虫体对枯草杆菌蛋白酶、胃蛋白酶或木瓜蛋白酶没有明显影响。以偶氮白蛋白为底物可证明胰蛋白酶的失活，但失活的酶对苯甲酰-DL-精氨酸-对硝基苯胺、对甲苯磺酰-L-精氨酸甲酯（低分子量合成胰蛋白酶底物）和对硝基-对胍基苯甲酸酯（一种活性位点滴定剂）仍保留完全的催化活性。在加热、冷冻和解冻或酶的长时间透析条件下，失活是不可逆的。通过阳离子和SDS-聚丙烯酰胺凝胶电泳以及凝胶色谱法对失活的3H-胰蛋白酶进行分析，未能表明与失活酶相关的高分子量胰蛋白酶抑制剂的存在；失活酶热变性后，未检测到低分子量的、可解离的抑制剂。在脉冲标记的虫体存在下孵育后对胰蛋白酶的分析也未能证明与失活酶相关的任何虫源抑制剂的存在。数据表明，失活是酶分子中微小结构或构象变化的结果，这种变化使酶对蛋白质底物部分（而非完全）失活。
