Anticoagulant Activity of the Trypsin Inhibitor from Soya Bean Flour

Abstract

We have observed that the trypsin inhibitor from unheated soya bean flour 1 2 has marked anticoagulant activity on human whole blood, recalcified plasma and recalci-fied plasma to which an excess of thromboplastin is added. (Table I). However, the soya bean inhibitor has no antithrombic activity. We have also observed that this material inhibits the proteolytic enzyme of blood plasma, 3 which may play a role in the coagulation of blood. This is true whether the plasma enzyme has been activated by chloroform treatment or by the addition of streptolysin. 4 5

A crude preparation of inhibitor was obtained by the method of Ham et al. 1 An excess of potassium oxalate was added to the acetone free material in order to precipitate the calcium. The solution was dialyzed 48 hours against running tap water. It was rendered isotonic by addition of NaCl and brought to pH 7.4 by NaOH N/10. The results obtained with the crude material were confirmed with a purified preparation 4 times recrystallized, 2 secured through the courtesy of Dr. Moses Kunitz.

All experiments were conducted at pH 7.2-7.4 on human blood, citrated plasma and fibrinogen, in imidazole buffer, at 37°C. The streptolysin was a dry powder, dissolved in saline.∗, 5 Control experiments showed that the anticlotting and antiproteolytic activity were not due to the small amount of salt present in the crystalline preparation and that the addition of an excess of calcium did not modify the anticlotting activity. Autoclaving of the crude material at 120° C for 20 minutes completely abolished the anticoagulant activity and almost completely the antiproteolytic activity.

These facts represent a new instance of the inhibition of the clotting of blood by trypsin inhibitors. 6 , 7