Antithrombin III is a single chain glycoprotein with a molecular weight of 58 kDa. It is a member of the serine protease inhibitor super family and is considered to be the most important inhibitor in the coagulation cascade. ATIII inhibits a wide spectrum of serine proteases including thrombin, factors IXa, Xa and XIa, kallikrein, plasmin, urokinase, C1-esterase, and trypsin. Description: Human plasma. Alternative Names: ATIII protein, AT III protein, AT 3 protein, AT3 protein, Antithrombin 3 protein