The Isolation of a Potent Plasma Kallikrein with Weak Plasminogen Activator Activity

Kallikrein was isolated from human plasma by the following procedures: removal of euglobulins at pH 5.3; QAE Sephadex chromatography: gel filtration on Sephadex G-150 and G-100. The partially purified preparation was then freed of contaminants by running it down a column of Sepharose-4B to which had been linked antibodies to IgG and pre-PTA. Pre-kallikrein and kallikrein activities were monitored during the fractionation procedures using a new synthetic chromogenic substrate for plasma kallikrein (Chromozyme-PK, Penta-pharm, Basle, Switzerland). 5 mg of enzyme was obtained with a specific activity of 3.75 Chromozyme PK (CPK) units/mg at 22° (yield = 9.5%: purification factor = 6250) and the yield of kinin from heated plasma was 1.79 μg/CPK unit/min. The kallikrein exhibited very weak plasminogen activator activity when tested on fibrin plates and in fibrin clot lysis assays(1 CPK unit =0.133 CTA units urokinase). Some other properties of the enzyme are discussed.