Abstract
Aluminum hydroxide adsorbed guinea pig plasma was fractionated by QAE Sephadex A‐50. Fractions correcting the clotting defect in Factor XII‐deficient plasma (without having an effect on Factor XI‐deficient plasma) were pooled and rechromatographed twice through Sephadex G‐200. By gel filtration Factor XII had an approximate molecular weight of 130 000 – 140 000. Its approximate isoelectric point was 5.2. The partially purified Factor XII had no effect on prekallikrein, but upon trypsinization or adsorption to and desorption from celite, generation of prekallikrein activator was induced. Prekallikrein activator added to prekallikrein activated this pre‐enzyme, which then hydrolyzed BAEe and liberated kinin from heated plasma.
An incidental finding was the recovery of an inhibitor of kallikrein. It eluted immediately after the excluded peak by anion exchange chromatography. It was passed twice through Sephadex G‐200 and had an approximate molecular weight of 100 000. The kallikrein inhibitor had a pl of 4.7–5.3. It was found to be heat‐resistant up to 80°C and resistant to acidification (pH 1.4). Under the conditions obtained the inhibitor also inactivated plasmin, trypsin and thrombin.