Activation of coagulation factor V by a platelet protease.
Activation of coagulation factor V by a platelet protease.
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血小板蛋白酶激活凝血因子 V。
DOI：
10.1172/jci110697
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
Majerus,PW
中科院分区：
文献类型：
--
作者：
Kane,WH;Mruk,JS;Majerus,PW
因子V必须转化为因子Vain才能结合到高亲和力的血小板表面位点并参与凝血酶原活化。Osterud等人（10）提出的数据表明，人类血小板含有一种活化形式的因子V和一种因子V激活剂。我们发现当血小板被冷冻、解冻或超声破坏时释放的因子V被凝血酶激活3- 10倍，因此作为相对无活性的前因子而不是以活性形式的因子V储存。我们将纯化的因子V与从因子V缺乏患者获得的冷冻和解冻的因子V缺陷血小板（109个血小板/ml）孵育，其比活性为140±30 U/mg。因子V的比活性最高可达740±240 U/mg（三次实验的平均值±标准差）。部分活化的V因子与凝血酶孵育后，其比活性进一步提高至1440±280 U/mg，与单独用凝血酶活化的V因子的活性（1540±60 U/mg）相似。93 μM的丹酰精氨酸-4-乙基哌替啶酰胺对血小板因子V激活剂没有抑制作用，说明它不是凝血酶。当加入丹酰精氨酸-4-乙基哌啶酰胺以抑制凝血酶进一步作用的凝血酶刺激血小板与125标记的因子V孵育时，没有检测到因子V分子的蛋白水解。在这些条件下，我们未能检测到因子V的激活，这表明血小板蛋白酶中小于4%是由凝血酶释放的。血小板亚细胞分馏表明活化因子V的血小板蛋白酶在可溶性分馏中。当血小板蛋白酶作用形成的因子与血小板一起孵育时，mr = 105,000, 87,000和78,000的肽结合到血小板表面。所有三种放射性标记的肽都被凝血酶作用下形成的未标记的凝血因子从血小板中取代。结合的化学计量学表明105,000道尔顿肽与87,000或78,000道尔顿肽相关。78,000道尔顿肽结合具有更大的亲和力，可能是因子无效凝血试验活性的主要原因。在正常止血过程中，血小板蛋白酶是否在凝血酶形成之前激活V因子，仍有待确定。图片
Factor V must be converted to Factor Vain order to bind to a high affinity platelet surface site and participate in prothrombin activation. Osterud et al. (10) presented data that suggested that human platelets contain an activated form of Factor V and a Factor V activator. We find that the Factor V released when platelets are disrupted by freezing and thawing or sonication is activated 3- to 10-fold by thrombin as determined by coagulation assay and is therefore stored as the relatively inactive procofactor rather than in the active form Factor Va.We incubated purified Factor V, which had a specific activity of 140±30 U/mg, with Factor V-deficient frozen and thawed platelets (109platelets/ml) obtained from a patient with Factor V deficiency. The specific activity of the Factor V increased to a maximum of 740±240 U/mg (mean±SD of three experiments). When this partially activated Factor V was incubated with thrombin its specific activity increased further to 1,440±280 U/mg, which is similar to the activity of Factor V activated with thrombin alone (1,540±60 U/mg).The platelet Factor V activator is not inhibited by dansyl arginine-4-ethylpiperidine amide, 93 μM, indicating that it is not thrombin. When thrombin-stimulated platelets, to which dansyl arginine-4-ethylpiperidine amide had been added to inhibit the further action of thrombin, were incubated with125-labeled Factor V, there was no detectable proteolysis of the Factor V molecule. Our failure to detect activation of Factor V under these conditions suggests that <4% of the platelet protease is released by thrombin. Subcellular fractionation of platelets indicates that the platelet protease that activates Factor V is in the soluble fraction.When Factor Vaformed by the action of platelet protease is incubated with platelets, peptides withMr= 105,000, 87,000, and 78,000 bind to the platelet surface. All three radiolabeled peptides are displaced from platelets by unlabeled Factor Vaformed by the action of thrombin. The stoichiometry of binding suggests that the 105,000-dalton peptide is associated with either an 87,000- or a 78,000-dalton peptide. The 78,000-dalton peptide binds with greater affinity and probably accounts for the bulk of the activity of Factor Vain coagulation assays. Whether or not the platelet protease serves to activate Factor V before thrombin formation during normal hemostasis remains to be determined.Images