Purification and partial characterization of plasminogen activator from human uterine tissue

A procedure was developed for the purification of a plasminogen activator from human uterine tissue. It involves six consecutive steps: (1) extraction of the plasminogen activator from delipidated uterine tissue with 0.3 M potassium acetate buffer, pH 4.2; (2) ammonium sulphate precipitation; (3) zinc chelate-agarose chromatography; (4) n-butyl-agarose chromatography; (5) concanavalin A-agarose chromatography; and (6) gel filtration on Sephadex G-150. The specific activity of the final plasminogen activator preparation was increased by a factor 4500 as compared with the crude extract. The purified plasminogen activator showed a strong tendency to adsorb to surfaces. This could be effectively prevented by Tween-80. The molecular weight of the plasminogen activator was 64 000 as estimated by gel filtration in 1.0 M NaCl and 69 000 as estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The plasminogen activator consisted of two chains (molecular weights 31 000 and 38 000) connected by disulphide bridges. The smallest chain contained the serine residue of the active site as deduced from the incorporation of the tritium label of [3H]diisopropylphosphofluoridate.