<prompt> Antithrombin is protein produced byLiverSpleenKidneyLung  <response>: Liver: 459- 992 H 18th editionANTI THROMBIN or anti thrombin III is the major plasma protease inhibitor of thrombin and the other clotting factors in coagulation. Synthesized in the liver and circulating in plasma at a concentration of 2.6 0.4mm antithrombin acts as suicide substrate for its target enzymes. 