Binding of urokinase to plasma proteinase inhibitors

Abstract

¹²⁵I-labelled urokinase was incubated with plasma and plasminogen free plasma, and the incubation mixtures were analysed by agarose gel electrophoresis. Autoradiography demonstrated that non-reacted urokinase remained around the slit and that complex-formation with inhibitors altered the migration and resulted in two bands, a major one and a minor one. Crossed immuno electrophoresis combined with autoradiography showed that the major band contained a complex between α₂-_-antiplasmin and urokinase. The minor band contained a complex between α₂-_-macroglobulin and urokinase. Also di-isopropylfluoro-phosphate-inactivated urokinase was bound to α₂-_-macroglobulin but not to α₂-_-antiplasmin. Thus, an intact active site of urokinase is not necessary for complex formation with α₂-_-macroglobulin.