Purification of antithrombin III by affinity chromatography

Human antithrombin III has been purified from plasma by affinity chromatography on heparin-Sepharose gel. After further fractionation on DEAE-Sephadex and Sephadex G 200 a homogeneous preparation of molecular weight 67 000 was obtained. Amino acid analysis showed that cystine and cysteine were absent. The carbohydrate content was found to be 15.2 %, and N-terminal analysis gave only histidine. Antithrombin III presumably consists of a single polypeptide chain without disulphide bridges. The pure preparation showed both progressive antithrombin activity and heparin cofactor activity.