Purification of Proteolytic Enzymes in Plasma and Other Enzymes by Affinity Chromatography

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Affinity chromatography depends on the specific affinity and adsorption of substance for the ligand bound to carrier matrix. Substrate, inhibitor and many other compounds are used as the ligand. In our laboratory, various compounds with low molecular weight and high molecular one were used as ligand, and applied to the affinity chromatography of trypsin, plasmin, plasma kallikrein, thrombin, thymidine kinase and leucine aminopeptidase. Based on our previous inhibition experiments on trypsin-like enzymes, such as trypsin, plasmin, kallikrein and thrombin, hexyl Nα-(ε-aminocaproyl)-homoargininate was coupled with agarose (Sepharose 4B), and applied to the affinity chromatography of these enzymes. To this agarose column trypsin was adsorbed and eluted with 0.1M acetic acid, although chymotrypsin was not adsorbed. In order to purify plasmin, EDTA-treated euglobulin fraction activated with streptokinase was applied on the agarose column equilibrated with 0.1M borate buffer containing 0.5M NaCl, pH 8.0, washed with the same buffer, and eluted with 0.1M acetic acid. Specific activity was raised from 19 to 108. Because hexyl Nα-(ε-aminocaproyl)-homoargininate has a positively charged guanidino group and hydrophobic group, the agarose coupled with this compound functions as an anion-exchanger, and may adsorb various proteins nonspecifically. In order to avoid such nonspecific adsorption, plasmin solution was applied to the column equilibrated with 0.1M phosphate buffer containing 0.2M NaCl, 10mM benzylamine and 5mM EDTA, pH 7.4, washed with the same buffer, and eluted with 0.1M acetic acid. Specific activity was raised from 14 to 305. At the same experimental condition, thrombin (Mochida Pharm. Co.) was applied to the agarose column, and eluted with 0.1M acetic acid. Specific activity was raised from 65 to 300. On the other hand, plasma kallikrein activated with acetone was not adsorbed at 0.1M borate buffer containing 0.2M NaCl, pH 8.0, but adsorbed at 0.1M borate buffer. The specific activity was not raised in either low or high ionic strength. Thymidine kinase preparation, which was prepared by streptomycin treatment and heat treatment at 60° for 3 min of Yoshida sarcoma homogenate was applied on agarose coupled with 5'-amino-5'-deoxythymidine, which is a synthetic inhibitor of thymidine kinase, washed with 0.1M Tris-0.2M NaCl buffer, pH 8.0, and eluted with the same buffer containing 1.5M NaCl. Thus, thymidine kinase was purified 5100 folds from homogenate. The yield was 45 per cent. In order to purify leucine aminopeptidase from human liver homogenate, leucine amide was used as a ligand. Before application on affinity column, the homogenate was sonicated and digested with bromelain at 37° for 30min. The supernatant was applied on the agarose column at 10mM phosphate buffer, pH 7.5, and eluted with 30mM of the buffer. Because of nonspecific adsorption of various proteins, the raise of specific activity was 4.8-folds. Since plasmin hydrolyzes fibrinogen, fibrin and casein, EDTA-treated euglobulin fraction activated with streptokinase was applied on fibrinogen-agarose column, and eluted with 0.1M acetic acid. Specific activity was raised to 3.5-folds, however, plasminogen was also adsorbed on this column and eluted as did plasmin. These results indicate that the adsorption of human plasmin on this column does not depend on its specific adsorption. One molecule of human plasminogen and plasmin combines with one molecule of streptokinase, and forms plasminogen- or plasmin-streptokinase complex. By the adsorption of EDTA-treated human euglobulin fraction on streptokinase-agarose column and elution with 6M urea, highly purified human plasmin, about 70per cent purity, was obtained at 78per cent yield.
Japan Society of Clinical Chemistryの論文

Purification of Proteolytic Enzymes in Plasma and Other Enzymes by Affinity Chromatography

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