Kinetics of Human Blood Coagulation Induced by Trypsin

Summary

1. Trypsin is a potent activator of purified human serum factor X. In the presence of calcium the activation was greatly enhanced.

2. Trypsin did not activate purified human serum factor VII or crude human plasma factor V, with or without calcium.

3. A new trypsin inhibitor, Benzamidine-HCl (shown to be superior to soybean trypsin inhibitor) was used. The Benzamidine-HCl - trypsin complex did not interfere in the clotting system, whereas the soybean trypsin inhibitor-trypsin complex did.

4. Benzamidine-HCl was used to inactivate the trypsin at any desired stage during the activation of factor X.

5. The trypsin activated factor X was found to be very stable.

6. In the presence of activated factor X, factor V, cephalin and calcium, a very potent prothrombin activator was formed.

7. An apparent time-consuming reaction was observed when activated factor X was incubated with factor V in the presence of calcium, which required the subsequent addition of cephalin to convert prothrombin to thrombin.

8. The trypsin clotting mechanism is analogous to the clotting of blood by Russell’s viper venom.

^* Present address: Department of Biochemistry, University of Washington, Seattle, Wash. (USA).

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