Kortt A A
Biochim Biophys Acta. 1980 Jul 24;624(1):237-48. doi: 10.1016/0005-2795(80)90243-3.
A new inhibitor of bovine alpha-chymotrypsin has been isolated from winged bean seed. The inhibitor was purified to homogeneity by affinity chromatography on chymotrypsin-Sepharose, following the removal of the trypsin inhibitors on trypsin-Sepharose. The inhibitor has a molecular weight of approx. 21,000 and amino acid analysis showed that it contains four half-cystine residues, lacks methionine, and is rich in aspartic acid, glutamic acid, valine and leucine. The inhibitor does not inhibit bovine trypsin in the standard inhibitor assay and does not bind to trypsin-Sepharose at ph 8.0. Inhibition data show that 1 mol of inhibitor inhibits 2 mol of alpha-chymotrypsin to form a 1:2 complex. The inhibition, however, is characterized by substrate induced dissociation of the complex and complete inhibition, even at high inhibitor concentration, is not attained. The inhibitor-chymotrypsin complex is stable at pH 8.0 and was isolated by gel-filtration on Sephadex G-100. An apparent molecular weight of approx. 70,000 was obtained for the complex, measured by gel filtration and ultracentrifugal analysis, consistent with a 1:2 molar stoichiometry.
从四棱豆种子中分离出一种新型牛α-糜蛋白酶抑制剂。在通过胰蛋白酶-琼脂糖除去胰蛋白酶抑制剂后，利用胰凝乳蛋白酶-琼脂糖亲和层析将该抑制剂纯化至同质。该抑制剂的分子量约为21,000，氨基酸分析表明它含有四个半胱氨酸残基，不含蛋氨酸，且富含天冬氨酸、谷氨酸、缬氨酸和亮氨酸。在标准抑制剂测定中，该抑制剂不抑制牛胰蛋白酶，在pH 8.0时也不与胰蛋白酶-琼脂糖结合。抑制数据表明，1摩尔抑制剂抑制2摩尔α-糜蛋白酶形成1:2复合物。然而，这种抑制的特点是底物诱导复合物解离，即使在高抑制剂浓度下也无法实现完全抑制。抑制剂-糜蛋白酶复合物在pH 8.0时稳定，并通过Sephadex G-100凝胶过滤分离。通过凝胶过滤和超速离心分析测得该复合物的表观分子量约为70,000，这与1:2的摩尔化学计量比一致。
