[Procedures for the isolation and characterization of human antithrombin III]

Antithrombin III, the most important inhibitor of activated coagulation factors (IIa, IXa, Xa, XIa, XIIa) was isolated from human plasma by affinity chromatography. The biochemical characterization of this highly purified inhibitor showed, that is was uniform by means of HPLC and PAA gradient gel electrophoresis. The molecular weight was determined to 70000 daltons and the isoelectric point was pH 4,5. The inhibition of factor Xa by AT III had been proofed as competitive by kinetic studies. AT III works as a "dead end inhibitor". Heparin seems to form a ternary complex with AT III and activated coagulation factors, so acting as a catalyst. The therapeutic value of AT III-concentrates will be discussed.