Bouma B N, Miles L A, Beretta G, Griffin J H
Biochemistry. 1980 Mar 18;19(6):1151-60. doi: 10.1021/bi00547a018.
Human plasma prekallikrein was purified from normal plasma. The purified prekallikrein appeared homogeneous on polyacrylamide gels in the presence of sodium dodecyl sulfate and mercaptoethanol and gave two protein bands with approximate Mr 85 000. Proteolytic activation of prekallikrein by purified human beta-factor XIIa (Mr 28 000 form) resulted in the formation of kallikrein. The apparent molecular weight of kallikrein determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the absence of mercaptoethanol was identical with that of prekallikrein; reduction of kallikrein yielded a heavy chain of Mr 52 000 and two light chains of Mr 42 000 and 37 000. The appearance of kallikrein activity was directly correlated with the limited proteolysis due to beta-factor XIIa. Kinetic and immunologic studies demonstrated that plasma prekallikrein is a factor XII dependent plasminogen proactivator. The rate constant for the inactivation of prekallikrein by diisopropyl phosphofluoridate was similar to that previously reported for trypsinogen. This observation raises the possibility that low intrinsinc catalytic activity of prekallikrein may play a role in the initiation of the intrinsic blood coagulation pathway.
人血浆前激肽释放酶从正常血浆中纯化得到。在十二烷基硫酸钠和巯基乙醇存在的情况下，纯化的前激肽释放酶在聚丙烯酰胺凝胶上呈现均一性，并给出两条分子量约为85000的蛋白带。纯化的人β-因子XIIa（分子量28000的形式）对前激肽释放酶的蛋白水解激活导致激肽释放酶的形成。在不存在巯基乙醇的情况下，通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳测定的激肽释放酶的表观分子量与前激肽释放酶相同；激肽释放酶的还原产生一条分子量52000的重链和两条分子量42000和37000的轻链。激肽释放酶活性的出现与β-因子XIIa引起的有限蛋白水解直接相关。动力学和免疫学研究表明，血浆前激肽释放酶是一种依赖因子XII的纤溶酶原激活剂。二异丙基氟磷酸酯使前激肽释放酶失活的速率常数与先前报道的胰蛋白酶原的速率常数相似。这一观察结果增加了前激肽释放酶低内在催化活性可能在凝血内源性途径启动中起作用的可能性。
