RESISTANCE OF ECARIN THROMBIN TO INHIBITION BY ANTITHROMBIN-III - DUAL ROLE FOR ECARIN

The thrombin produced from prothrombin by ecarin, the coagulant fraction of Echis carinatus venom, was found to be insensitive to inhibition by heparin and antithrombin III in plasma containing ecarin. However, in the absence of ecarin, the purified ecarin-thrombin was inhibited by heparin in plasma, and also by pure antithrombin III. The protective effect of ecarin, in preventing the inhibition of ecarin-thrombin by antithrombin III, was concentration dependent. On SDS-polyacrylamide gel electrophoresis both Xa-thrombin and ecarin-thrombin formed complexes with antithrombin III. It appears that ecarin has at least two functions; it can activate prothrombin, and also prevent the inactivation of ecarin-thrombin by antithrombin III. © 1979.