Home » 科技术语 » Tissue Factor|Thromboplastin | 组织因子

Tissue Factor|Thromboplastin | 组织因子

250px-Protein_F3_PDB_1ahw[1].png 组织因子

是一个由263 个氨基酸残基组成的跨膜单链糖蛋白,分子量约为47 kDa。其中氨基端219 个氨基酸残基位于细胞膜外,紧随其后的23 个氨基酸残基则穿过细胞膜,其余21 个氨基酸残基位于细胞质内。正常情况下,组织因子位于血管壁外膜细胞,包绕血管的成纤维细胞,肝、脾、肾等器官的纤维囊,及皮肤外层的表皮细胞、肾小球上皮细胞、脑皮质、心肌细胞、肺泡巨噬细胞、胃肠道壁、部分生殖泌尿道和子宫内膜基质细胞中,而在血管中膜或内膜层却很稀少。因此在正常情况下组织因子不存在于循环中或不与循环血液接触,只有当血管壁的完整性遭到破坏时TF 才暴露于循环血液,通过激活凝固级联反应发挥止血作用。

组织因子通过与因子Ⅶ/ Ⅶa 结合而启动血液凝固级联反应。而且TF 依靠其与细胞膜的紧密结合发挥"锚"作用,使生理性凝血过程局限于损伤部位,而不从血液凝固的起始部位向远处播散。TF 启动血液凝固的过程是,当细胞表面表达的TF 暴露于血浆蛋白时,TF 就会与其有高亲和力的因子Ⅶ(factor Ⅶ,F Ⅶ) 相粘连。游离的因子Ⅶa (F Ⅶa) 和/或已形成的TF2 Ⅶa 复合物可激活TF2F Ⅶ复合物转变成TF2Ⅶa 复合物,而且TF2 Ⅶa 复合物可进一步激活游离F Ⅶ。这些机制被称为TF 介导F Ⅶ自身激活。TF2 Ⅶa 复合物可迅速催化因子Ⅹ的激活。另外,TF2 Ⅶa 能以较低的速率激活因子Ⅸ,激活的因子Ⅸa 在辅因子Ⅷ的存在下可激活因子Ⅹ转变成因子Ⅹa ,这些过程最终导致凝血酶产生 。凝血酶进而催化纤维蛋白原转变成纤维蛋白并聚合成纤维蛋白血块。即TF 可同时激活凝血因子Ⅸ和Ⅹ,启动内、外源性两种凝血酶联放大反应,在血栓形成过程中起着重要作用。但是在生理浓度时TF 和F Ⅶ单独存在都不具有促凝活性。

(From http://baike.baidu.com/view/2889898.htm)

Tissue factor

also called platelet tissue factor, factor III, thrombokinase, or CD142 is a protein present insubendothelial tissue, platelets, and leukocytes necessary for the initiation of thrombin formation from the zymogen prothrombin. An incorrect synonym is thromboplastin. Historically, thromboplastin was a lab reagent, usually derived from placental sources, used to assay prothrombin times (PT time). Thromboplastin, by itself, could activate the extrinsic coagulation pathway. When manipulated in the laboratory, a derivative could be created called partial thromboplastin. Partial thromboplastin was used to measure the intrinsic pathway. This test is called the aPTT, or activated partial thromboplastin time. It was not until much later that the subcomponents of thromboplastin and partial thromboplastin were identified. Thromboplastin is the combination of both phospholipids and tissue factor, both needed in the activation of the extrinsic pathway. However, partial thromboplastin is just phospholipids, and not tissue factor. Tissue factor is not needed to activate the intrinsic pathway. (From:http://en.wikipedia.org/wiki/Tissue_factor)

Leave a Reply