TAMe esterase activity resulting from blood thromboplastin formation

Abstract

TAMe esterase activity levels have been determined on a) purified coagulation factors essential for thromboplastin (TPN) formation, b) various intermediate products formed in the presence of calcium and phospholipid, and c) complete blood thromboplastin. The level of esterase activity was found to increase as TPN formation proceeded through various intermediate stages to the final active product. The esterase activities of intermediate products I and II were practically completely inhibited by soybean trypsin inhibitor (SBTI), whereas that of blood thromboplastin was inhibited only partially. Interaction of product II with plasma Ac-globulin resulted in the most marked increase in esterase activity. The observations made suggest that this increased and SBTI-insensitive activity is not due to the presence of either thrombin or serum Ac-globulin (factor VI). It has been concluded that the observed TAMe esterase activity is due to blood thromboplastin itself and that the latter resembles Milstone's thrombokinase.