A single-step method for the isolation of antithrombin III

A single-step method is described for the isolation of a highly purified antithrombin III (AT III) concentrate at a recovery of over 30% using affinity chromatography on heparin-Sepharose (HS). The polyethylene glycol precipitation step frequently employed in the preparation of AT III concentrates for clinical use has been eliminated and purification is accomplished entirely by optimizing the salt concentration in the HS washing buffer to enhance the desorption of impurities prior to elution of AT III. Pasteurization of the AT III concentrate in the presence of 0.5 M sodium citrate to minimize the risk of hepatitis decreases the recovery by about 20% and induces changes in the patterns obtained by polyacrylamide gel electrophoresis and by crossed immunoelectrophoresis in heparinized agarose gel.