Kaplan A P, Austen K F
J Exp Med. 1972 Dec 1;136(6):1378-93. doi: 10.1084/jem.136.6.1378.
The conversion of the plasminogen proactivator to plasminogen activator by activated Hageman factor or its fragments has been recognized as an essential step in the conversion of plasminogen to plasmin. The plasminogen proactivator has been completely separated from prekallikrein and pre-PTA, two other proenzyme substrates of activated Hageman factor or its fragments. Plasminogen proactivator, free of any contaminating proteins as assessed by disc gel electrophoresis or isoelectric focusing, revealed a single band with an isoelectric point of 8.9 corresponding in position to the Hageman factor activatable material eluted from replicate unstained gels. After conversion of plasminogen proactivator by Hageman factor fragments to the plasminogen activator, the active site of the plasminogen activator is not inhibited by C1INH and is thus readily distinguished from that of kallikrein or PTA. The plasminogen activator is susceptible to inactivation by DFP while the plasminogen proactivator is not, as has been the case for esterases having a serine in the active site. Its interaction with plasminogen is inhibited by epsilon-aminocaproic acid.
活化的哈格曼因子或其片段将纤溶酶原激活剂转化为纤溶酶原激活物，这一过程被认为是纤溶酶原转化为纤溶酶的关键步骤。纤溶酶原激活剂已与前激肽释放酶和前激肽原激活剂完全分离，后两者是活化的哈格曼因子或其片段的另外两种酶原底物。通过圆盘凝胶电泳或等电聚焦评估，不含任何污染蛋白的纤溶酶原激活剂显示出一条等电点为8.9的单一谱带，其位置与从重复的未染色凝胶中洗脱的哈格曼因子可激活物质相对应。在哈格曼因子片段将纤溶酶原激活剂转化为纤溶酶原激活物后，纤溶酶原激活物的活性位点不受C1INH抑制，因此很容易与激肽释放酶或激肽原激活剂的活性位点区分开来。纤溶酶原激活物易被二异丙基氟磷酸酯（DFP）灭活，而纤溶酶原激活剂则不然，活性位点含有丝氨酸的酯酶也是如此。其与纤溶酶原的相互作用受ε-氨基己酸抑制。
