Plasminogen-free proactivator B obtained from human plasma.

As reported in the previous paper by the authors, two kinds of precursor of plasminogen activator were presented by gel filtration method, which were named proactivator A and proactivator B.1) However the former fraction did not contain plasminogen, the latter on the other hand always coexisted with plasminogen, which seemed to be difficult to separate. Therefore, a question arises that fibrinolytic activity demonstrated by adding streptokinase (SK) to proactivator B fraction (with plasminogen) might not be mediated by the activation of proactivator but caused directly by the activation of plasminogen by SK. To resolve the question it is required that proactivator B can be obtained which was separated from plasminogen, and that fibrinolysis should be examined by using thus obtained proactivator B. The results in this paper are to prove that fibrinolytic activity demonstrated by proactivator B fraction is also mediated by an activator converted from proactivator B as in the case of proactivator A.