Studies on Protein Fractions Isolated from Human Plasma

S ummary . Fractions of human plasma separated by precipitation with cold ether and ethanol were examined for a number of protease and esterase activities. Plasminogen, kallikrein, increased vascular permeability, thrombin and TAMe esterase were concentrated in fraction G 2 / i R, a lipo-protein fraction containing a mixture of alpha and beta globulins and a gamma-M globulin, which also contained activated coagulation contact factors. ATEe esterase was concentrated in G 2 / i R and fibrinogen. Kinin-ase and TAMe esterase were also found in G 2 / 2 a mixture of alpha, beta and gamma globulins.
Tests of fractions of G 2 / i R separated by chromatography confirmed the findings of Kagen et al , (1963) and showed that kallikrein was a gamma-M globulin. Vascular permeability activity, but not kininogenase activity was removed by high-speed centrifugation from this fraction.
Fractions G 2 / i R, G 2 / 2 and to a lesser extent G 3 contained a substance which induced kininogenase activation in intact plasma, but was not identified as PF, plasmin or activated contact factor and had no esterase activity.
Kininogenase activity was associated with contaminants of fibrinogen and gamma globulin concentrates and absent from albumin. In fractions prepared by large-scale methods, only those made from G 2 are likely to contain sufficient kininogenase to cause a clinical reaction. Kininogenase was not adsorbed by Al(OH)³ gel or C^a3(PO⁴)² and would not contaminate clotting factors prepared from G².