Heparin-sensitive and nonsensitive forms of thrombin.

Two forms of thrombin (Ts-thrombin and Tp-thrombin) were found with respect to heparin sensitivity. Inactivation of Ts-thrombin by antithrombin-III was facilitated with heparin, whereas inactivation of Tp-thrombin was not. Both thrombins were bound to heparin in a Sephadex G-200 gel filtration experiment. Ts-thrombin proved to be more stable and was better protected by heparin against heat inactivation of 54 degrees C than Tp-thrombin.