Evidence that antithrombin and the inhibitor of activated Staart-Prower factor are separate entities

Evidence has been presented to show that in spite of the close similarities between the natural inhibitor of activated Stuart-Prower factor (Anti Xa) and antithrombin, they are separate entities. Use has been made of the fact that both inhibitors inactivate their respective enzymes by binding them and that their activity can be saturated in plasma to eliminate either inhibitor activity and show that the other one maintains its full activity. Furthermore by using radioactive isotope labelling and molecular sieve chromatography, it has been shown that neither inhibitor binds the other enzyme thus confirming that both inhibitors are separate entities.