Characterisation of the vascular plasminogen activator from the pig ear

Spontaneously released plasminogen activator after perfusion with 0.9% NaCl of isolated pig ear was purified by affinity chromatography on Heparin-Sepharose. The molecular weight of the plasminogen activator is about 60,000 Daltons, the isoelectric point lies at pH 7.6. The enzyme is most stable at neutral pH. At 37 degrees C it is stable for two hours. The activator did not show lytic activity either on heated or on PAMBA fibrin plates. The activity of the activator was inhibited by exposure to DFP and PMSF but not by exposure to TLCK and TPCK, suggesting that it is an enzyme with an active-site residue which belongs to the tissue-type activators.