Antithrombin III (AT III) is a single chain glycoprotein of molecular mass 58 kDa with four glycosylation sites and three intra-molecular disulfide bonds. AT III is normally present in human plasma at a concentration of appro, Xenopus/Amphibian,. 12.5 mg/dl. It is the major inhibitor of thrombin. Inactivation of thrombin by AT-III occurs by formation of a covalent bond resulting in an inactive 1:1 stoichiometric comple, Xenopus/Amphibian, between the two components. This antibody is specific for the native form of human AT III.