钙(Ⅱ)对尖吻蝮蛇毒抗凝血因子Ⅰ的抗凝血活性的影响

The Effect of Calcium (Ⅱ) on the Anticoagulant Activity of Anticoagulation FactorⅠfrom the Venom of Agkistrodon Acutus

皖南尖吻蝮蛇毒抗凝血因子I（ACF I）不具有酶的活性，通过与活化凝血因子X（FXa）结合成1：1的复合物来延长凝血时间。用高效液相色谱分析方法，发现 ACF I与FXa的结合反应依赖于 Ca2+浓度，ACF I与 FXa的最大结合反应所需要的 Ca2+浓度为 1mol· L-1 。稀土和过渡金属离子对ACF I的荧光有淬灭作用，相反， Ca2+对 ACF I的荧光有增强效应。 Ca2+对维持 ACF I的特定构象起着重要作用。 Ca2+诱导的 ACF I构象变化可能是ACF I与 FXa结合的必要条件。

Anticoagulation factor Ⅰ(ACF Ⅰ) from the venom of Agkistrodon acutus is a non-enzymatic anticoagulant and forms a l: 1 complex with activated coagulation factor X(FXa), and thereby prolongs the clotting time. It has been discovered from HPLC that the binding of ACF Ⅰ with FXa is dependent on the concentration of Ca2+ ions and the maximal binding of ACF I to FXa occurs at concentration of Ca2+ ions of Ⅰ mmol. L- 1. It is evident from the observation of metal ion-induced changes in the intrinsic fluorescence of ACF Ⅰ that ACF Ⅰ undergoes conformational changes upon binding of metal ions. In general, the intensity of fluorescence of ACF I decreases with the increases of ionic potentials(Z/ r) of bound metal ions in this protein. The lanthanide and transition metal ions give quenching effects on the fluorescence of ACF Ⅰ, while Ca2+ ions enhance the fluorescence of ACe Ⅰ. It can be deduced. from these results, that Ca2+ ions are essential for the specific conformation of ACF 1 and the conformational rearrangement of ACF Ⅰ induced by Ca2+ ions might be necessary for the binding of ACF Ⅰ with FXa.