Purification of a New Plasma Inhibitor of Kallikrein

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Abstract
Several inhibitors were separated from human serum by gel filtration on Sephadex G-200, and a new inhibitor was further purified by successive column chromatography on DEAE-ceflulose, hydroxylapatite and Sepharose-4B. By these procedures, 8.4mg of purified kallikrein inhibitor was obtained from 40 ml of human serum. The purified material was homogeneous, as judged by cellulose acetate electrophoresis, discelectrophoresis, and ultracentrifugation. It had an s20, value of 4.2 and an apparent molecular weight of 53,000, as measured by gel filtration on Sephadex G-200. The purified inhibitor was heat-labile and was unstable below pH 5.5, a pH value at which esterolysis of Nα-tosyl-L-arginine methyl ester and kinin formation by plasma kallikrein [EC 3. 4. 4. 211 are progressively inhibited. It also inhibited plasmin [EC 3. 4. 4. 14] and thrombin [EC 3.4.4. 13]. One mg of kallikrein inhibitor neutralized 5.3 TAME-esterolytic units of plasma kallikrein activated with acetone, 1.5 TAMEesterolytic units of plasmin activated with streptokinase and 5.6 TAME-esterolytic units of thrombin. On the other hand, it had only weak affinities for trypsin [EC 3.4. 4.4] and chymotrypsin [EC 3.4.4. 5]. This kallikrein inhibitor appeared to be a new inhibitor, distinct from the serum trypsin and Cl-esterase inhibitors described previously.

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