Deficiency of factor XII-dependent plasminogen proactivator in prekallikrein-deficient plasma

Normal human plasma contains a factor XII (Hageman factor)-dependent plasminogen proactivator in its gamma globulin fraction. On the basis of both fibrin plate and clot lysis assays, this plasminogen proactivator activity was shown to be absent from the gamma globulin fraction of prekallikrein (Fletcher factor)-deficient plasma of two unrelated patients. This observation suggests that factor XII-dependent plasminogen proactivator is identical to plasma prekallikrein.