Inhibition of urokinase by complex formation with human antithrombin III in absence and presence of heparin

Abstract

Human antithrombin III was purified from fresh human plasma by affinity chromatography on heparin-Sepharose, affinity chromatography on concanavalin A Sepharose, gel filtration on Ultrogel AcA 34, ion exchange chromatography on DEAE A-50 Sephadex and preparative agarose gel electrophoresis. The hydrolytic activity of urokinase (plasminogen activator from urine) on acetyl-glycyl-L-lysine methylester acetate (Ac-gly-lys-OMeAc) was inhibited by antithrombin III in a slow time-dependent manner. Heparin accelerated the reaction between activator and inhibitor. Inhibition of catalytic activity was associated with the formation of an 1:1 molar complex between activator and inhibitor as revealed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The complex was also demonstrated by crossed immunoelectrophoresis against anti-antithrombin III.