Acceleration of the reaction between thrombin and antithrombin III by non-stoichiometric amounts of heparin.

The accelerating effect of heparin on the reaction between purified human antithrombin and thrombin has been investigated by measuring the amount of thrombin inactivated during a short incubation of the enzyme with the inhibitor in the presence and absence of non-stoichiometric amounts of heparin. It was demonstrated that one molecule of heparin was able to promote the binding of a large number of antithrombin molecules to thrombin. Thus heparin may affect the rate of the inactivation of thrombin by antithrombin in a catalytic manner.