Shieh B H, Travis J
J Biol Chem. 1987 May 5;262(13):6055-9.
Human alpha 2-antiplasmin rapidly forms a stable, equimolar complex with either its target enzyme, plasmin, or with trypsin. Perturbation of the inhibitor-trypsin complex results in peptide bond cleavage at the reactive site of the inhibitor with the concomitant release of a small peptide fragment which apparently represents the carboxyl-terminal segment of the inhibitor. Sequence analysis of this fragment, together with that of an overlapping peptide obtained by treatment of native inhibitor with either Staphylococcus aureus V8 proteinase or human neutrophil elastase, yields data which indicate that the reactive site of alpha 2-antiplasmin encompasses a P1-P'1 Arg-Met sequence. However, unlike alpha 1-1-proteinase inhibitor which has a Met residue in the P1-position, oxidation of alpha 2-antiplasmin has no effect on its inhibitory activity toward either plasmin, trypsin, or chymotrypsin, indicating the lesser mechanistic importance of the P'1-residue during enzyme inactivation by this inhibitor.
人α2-抗纤溶酶能迅速与它的靶酶纤溶酶或胰蛋白酶形成稳定的等摩尔复合物。抑制剂-胰蛋白酶复合物受到干扰会导致抑制剂反应位点处的肽键断裂，同时释放出一个小肽片段，该片段显然代表抑制剂的羧基末端部分。对该片段进行序列分析，并结合用金黄色葡萄球菌V8蛋白酶或人中性粒细胞弹性蛋白酶处理天然抑制剂得到的重叠肽段进行分析，得到的数据表明α2-抗纤溶酶的反应位点包含一个P1-P'1精氨酸-甲硫氨酸序列。然而，与在P1位有一个甲硫氨酸残基的α1-抗胰蛋白酶抑制剂不同，α2-抗纤溶酶的氧化对其对纤溶酶、胰蛋白酶或胰凝乳蛋白酶的抑制活性没有影响，这表明在该抑制剂使酶失活的过程中，P'1残基的机制重要性较低。
