Cumin F, Vellaud V, Corvol P, Alhenc-Gelas F
INSERM U 36, Paris, France.
Biochem Biophys Res Commun. 1989 Sep 15;163(2):718-25. doi: 10.1016/0006-291x(89)92282-1.
Binding of the potent radiolabelled competitive inhibitor 3H RU 44403 to pure human kidney angiotensin-I converting enzyme was examined in equilibrium and non equilibrium conditions. Equilibrium dialysis experiments indicate that, despite the duplicated structure of the enzyme and the presence of two putative active sites, 3H RU 44403 interacts with a single high affinity (Kd = 0.44 +/- 0.05 x 10-9 M, n = 3) binding site. This suggests that only one of the two putative active sites is functional, and can bind substrates or inhibitors. Sodium chloride plays an essential role in the enzyme-inhibitor interaction. The formation of the complex is only slightly influenced by NaCl, but the kinetic of dissociation is dramatically dependent on NaCl concentration. In a Nacl free medium the complex is unstable and dissociates rapidly. These results are consistent with the hypothesis that chloride ion influences isomerization of the complex toward a more stable form.
在平衡和非平衡条件下，研究了强效放射性标记的竞争性抑制剂3H RU 44403与纯人肾血管紧张素I转换酶的结合情况。平衡透析实验表明，尽管该酶具有重复结构且存在两个假定的活性位点，但3H RU 44403与单个高亲和力（Kd = 0.44 +/- 0.05 x 10-9 M，n = 3）结合位点相互作用。这表明两个假定的活性位点中只有一个具有功能，能够结合底物或抑制剂。氯化钠在酶-抑制剂相互作用中起着至关重要的作用。复合物的形成仅受到氯化钠的轻微影响，但解离动力学却极大地依赖于氯化钠浓度。在无氯化钠的介质中，复合物不稳定且迅速解离。这些结果与氯离子影响复合物向更稳定形式异构化的假设一致。
