Asakura S, Matsuda M, Yoshida N, Terukina S, Kihara H
Division of Hemostasis and Thrombosis Research, Institute of Hematology, Jichi Medical School, Tochigi-Ken, Japan.
J Biol Chem. 1989 Aug 15;264(23):13736-9.
Upon incubation of antithrombin III with thrombin in the presence of a monoclonal antibody recognizing an epitope exposed on the heavy chain part of thrombin-cleaved two-chain antithrombin III, antithrombin III was preferentially cleaved by the enzyme as a substrate, rather than covalently complexed with the enzyme to form an equimolar, stable acyl complex. Once the stable acyl complex was formed between the enzyme and antithrombin III, however, no further liberation of two-chain antithrombin III was observed. Kinetic studies showed that heparin does not affect this reaction, although generation of thrombin-cleaved two-chain antithrombin III is apparently accelerated in accordance with the rate constant for heparin-enhanced thrombin-antithrombin III complex formation. Here we propose the term "switching antibody" for an antibody that triggers deacylation of an intermediate enzyme-inhibitor complex by switching the enzyme-inhibitor reaction from the major pathway of stable acyl complex formation to an alternative pathway of cleavage of the inhibitor as a substrate.
在存在识别凝血酶裂解的双链抗凝血酶III重链部分暴露表位的单克隆抗体的情况下，将抗凝血酶III与凝血酶一起温育时，抗凝血酶III作为底物优先被该酶裂解，而不是与该酶共价复合形成等摩尔的稳定酰基复合物。然而，一旦在酶和抗凝血酶III之间形成稳定的酰基复合物，就没有观察到双链抗凝血酶III的进一步释放。动力学研究表明，肝素不影响该反应，尽管根据肝素增强的凝血酶-抗凝血酶III复合物形成的速率常数，凝血酶裂解的双链抗凝血酶III的生成明显加速。在此，我们提出“转换抗体”这一术语，用于指通过将酶-抑制剂反应从稳定酰基复合物形成的主要途径切换到抑制剂作为底物的裂解替代途径来触发中间酶-抑制剂复合物脱酰化的抗体。
