Thrombin inhibitor, forms a non-covalent complex with thrombin at a molar ratio of 1:1, inhibits thrombin-induced platelet aggregation, and prolongs thrombin clotting time and activated partial thromboplastin time. It only minimally suppresses the amidolytic activity of thrombin. Expressed in salivary glands. The sequence shown is that of clone TR5. Belongs to the calycin superfamily. Triabin family.