粟種子α-アミラーゼインヒビターの精製と性質(B. 生活科学)

粟穀粒アセトンパウダーより, 食塩水抽出, 硫安塩析, DEAE-Sepharose CL-6Bイオン交換クロマトグラフィー, α-アミラーゼ-Sepharose 4Bアフィニティークロマトグラフィー, CM-Sephadex C-25イオン交換クロマトグラフィーにて蛋白質性のα-アミラーゼインヒビターを精製した。最終精製品は比活性で最初の抽出液の600倍以上となったがディスク電気泳動の結果では末だ均一ではなかった。本インヒビターは焦点電気泳動より等電点10,Sephadex G-75のゲル濾過より分子量19000を有すると示された。またpH7∿8で安定であり, ブタ膵臓とヒト唾液のα-アミラーゼに対し強力な阻害作用を示した。一方Bacillus subtilusα-アミラーゼは本インヒビターによって全く阻害を受けなかった。An α-amylase inhibitor was isolated and purified from the whole grain of foxtail millet, Setaria italica, by extraction with 1% NaCl, ammonium sulfate precipitation, and column chromatographies on DEAE-Sepharose CL-6B, α-amylase bound Sepharose 4B, and CM-Sephadex C-25. The specific activity of the finally purified sample was over 600-fold of that of the extract, but it still did not show a homogeneous behavior in disc polyacrylamide gel electrophoresis at pH4.0. The isoelectric focusing and Sephadex G-75 gel filtration of the crude preparation indicated that the inhibitor had an isoelectric point of 10 and a molecular weight of 19,000. This inhibitor was most stable from pH7 to 8,while it lost the activity as the pH was decreased to 2 or increased to 10. The inhibitor showed powerful inhibitor activities against porcine pancreatic and human salivary α-amylases, but failed to inhibit Bacillus subtilus α-amylase