摘要 本實驗之目的為應用超過濾膜反應系統生產分離大豆蛋白(SPI) 酵素水解物中，具有血管收縮素I轉換酵素 (Angiotensin I-converting enzyme；簡稱ACE) 抑制活性的胜?產物，並加以區分以提昇其活性；首先進行蛋白水解酵素的篩選，利用五種蛋白?alcalase、pepsin、trypsin、chymotrypsin和 flavourzyme水解SPI，測定其水解物的ACE抑制活性，篩選出alcalase-SPI水解物具有最高ACE抑制活性，並進一步探討該酵素水解SPI條件對ACE抑制活性之影響，結果顯示最佳水解條件為2.5%SPI添加1% alcalase於pH 9.0、溫度50℃的環境下進行水解4小時，即可顯著的將ACE抑制活性IC50降至 0.67 mg protein/ml。其次，將上述水解物利用超過濾膜系統進行區分，探討不同膜分子量限值 (molecular weight cut off; 簡稱MWCF) 對ACE抑制活性之影響，區分所用的膜包括30kDa、10kDa和1kDa MWCF，其中以使用10kDa MWCF所生產的10P產品其體外ACE抑制活性IC50值最低可達0.078 mg/ml。最後，探討體外腸胃道酵素消化試驗對10P產品的ACE抑制活性之影響，結果顯示此產品中的胜?對胃腸消化酵素的分解作用具安定性或經其分解後並未破壞ACE抑制活性胜?的胺基酸序列。 Abstract The purpose of this study was to produce and fractionate the ACE inhibitor from enzymatic hydrolysate of soy protein isolate (SPI) by using membrane reactor system. Five different proteolytic enzymes including alcalase, flavourzyme, trypsin, chymotrypsin and pepsin were used to hydrolyze SPI to produce the hydrolysates, individually. The result indicated that hydrolysis of SPI with alcalase produced the highest ACE inhibitory activity. Therefore, alcalase were selected for further study on optimization of hydrolysis conditions. The optimum conditions for alcalase to hydrolyzed SPI to produce ACE inhibitor were: E/S = 0.01, pH 9.0,hydrolysis temperature = 50℃and hydrolysis time = 4 hr. Under these conditions, The IC50 of SPI was significantly reduced from 66.4 to 0.67 mg protein/ml. Moreover, membranes with molecular weight cut-off (MWCF) from 30,000 to 1,000 daltons were used to fractionate the hydrolysate. The fraction obtained from the treatment of the hydrolysate by 10,000 daltones MWCF membrane could further reduce its IC50 from 0.67 to 0.078 mg protein/ml. The ACE inhibitory peptides derivied from SPI showed resistance to in vitro digestion by gastrointestinal proteases.
