The Kinin System of Human Plasma VI. The Action of Plasmin 1

Summary

Plasminogen was isolated from acid euglobulin by gel filtration through Sephadex G-200 and anion exchange chromatography on DEAE-Sephadex A-50. Nonspecific esterases were inactivated with DFP and the plasminogen was rechromatographed.

Plasmin (streptokinase activated plasminogen) was shown to act on kininogen (heated plasma), from which it released kinin. This was a slow process. Rapid kinin formation was achieved when plasmin liberated prekallikrein activator from partially purified activated Hageman factor (factor XIIa), which in turn acted on prekallikrein. The active kallikrein enhanced vascular permeability when injected intradermally into guinea pigs, hydrolyzed BAEe, and rapidly liberated kinin from heated plasma substrate.

It is concluded that plasmin in high concentrations liberates kinin directly from kininogen. However, in low concentrations (which prevail in vivo), when it functions as an activator, it acts not directly on prekallikrein, as postulated repeatedly, but probably by liberating prekallikrein activator from factor XIIa.