ACTIVATION OF FACTOR-VII BOUND TO TISSUE FACTOR - A KEY EARLY STEP IN THE TISSUE FACTOR PATHWAY OF BLOOD-COAGULATION
ACTIVATION OF FACTOR-VII BOUND TO TISSUE FACTOR - A KEY EARLY STEP IN THE TISSUE FACTOR PATHWAY OF BLOOD-COAGULATION
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DOI：
10.1073/pnas.85.18.6687
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发表时间：
1988-09-01
影响因子：
11.1
通讯作者：
RAPAPORT, SI
中科院分区：
文献类型：
--
作者：
RAO, LVM;RAPAPORT, SI
在组织因子依赖性血液凝固中形成的因子VII/组织因子复合物是否必须在其能够激活其底物因子X和因子IX之前被激活为因子VIIa/组织因子，这一直是一个难以回答的问题，因为底物一旦被激活，就会反向激活因子VII。我们早期的研究表明，人因子VII/组织因子不能激活因子IX。研究现已扩展到因子X的激活。用纯化的因子VII、X和组织因子制备反应混合物;在一些实验中加入抗凝血酶III和肝素以防止因子VII的反向激活。在含有因子VII或因子VIIa的反应混合物中，在与因子VII的初始30秒滞后之后，因子X以相似的速率被激活。在与因子VII的反应混合物中，在125 I标记的因子VII裂解为双链活化分子之前几分钟，建立了因子X的线性活化，这在凝胶图谱上是可证明的。添加抗凝血酶III和肝素阻断因子VII/组织因子对因子X的激活，但不阻断因子VIIa/组织因子对因子X的激活。当抗凝血酶III和肝素在其他试剂加入后1分钟加入时，因子VII/组织因子对因子X的激活未被阻断。这些数据表明，因子VII/组织因子不能在几分钟内激活可测量量的因子X。总体而言，我们的研究结果支持了这一假设，即通过微量Xa因子快速优先激活与组织因子结合的因子VII是组织因子依赖性凝血的关键早期步骤。
Whether the factor VII/tissue factor complex that forms in tissue factor-dependent blood coagulation must be activated to factor VIIa/tissue factor before it can activate its substrates, factor X and factor IX, has been a difficult question to answer because the substrates, once activated, back-activate factor VII. Our earlier studies suggested that human factor VII/tissue factor cannot activate factor IX. Studies have now been extended to the activation of factor X. Reaction mixtures were made with purified factor VII, X, and tissue factor; in some experiments antithrombin III and heparin were added to prevent back-activation of factor VII. Factor X was activated at similar rates in reaction mixtures containing either factor VII or factor VIIa after an initial 30-sec lag with factor VII. In reaction mixtures with factor VII a linear activation of factor X was established several minutes before cleavage of 125I-labelled factor VII to the two-chain activated molecule was demonstrable on gel profiles. Adding antithrombin III and heparin blocked activation of factor X by factor VII/tissue factor but not by factor VIIa/tissue factor. When the antithrombin III and heparin were added 1 min after the other reagents, factor VII/tissue factor activation of factor X was not blocked. These data suggest that factor VII/tissue factor cannot activate measurable amounts of factor X over several minutes. Overall, our results support the hypothesis that a rapid preferential activation of factor VII bound to tissue factor by trace amounts of factor Xa is a key early step in tissue factor dependent blood coagulation.