PROBLEM TO BE SOLVED: To provide protein decomposition product including a large amount of angiotensin-converting enzyme inhibiting active peptide which can be prepared by a simple method, easily handled as an edible product, and expected to have an excellent blood pressure lowering effect, from extraction residue (used tea leaves) produced by extraction of tea leaves or used tea leaves with water or hot water.SOLUTION: The steps are sequentially performed of extracting tea leaves or used tea leaves with alkali aqueous solution, adding acid to the produced extract to have a pH of 2 to 5 for precipitation of a protein fraction, decomposing the produced protein fraction with protease for stopping the enzyme reaction, and allowing the enzyme reaction liquid to have a pH of 2 to 5 for separating a peptide fraction soluble in acidic aqueous solution and an unreacted protein fraction through precipitation of the unreacted protein fraction. In the decomposing step using protease, neutral endopeptidase and acidic exopeptidase are employed to function.COPYRIGHT: (C)2014,JPO&INPIT【課題】茶葉あるいは茶殻を水乃至温水で抽出して得られる抽出残渣(茶殻)から調製方法が複雑でなく、食用として扱いやすく、優れた血圧降下作用が期待されるアンジオテンシン変換酵素阻害活性ペプチドを多く含有するタンパク質分解物を提供する。【解決手段】茶葉あるいは茶殻をアルカリ水溶液で抽出し、得られた抽出液に酸を加えてpH2から5にすることによりタンパク質画分を沈降させる工程及び、得られたタンパク質画分をタンパク質分解酵素で分解し酵素反応を停止した後に、酵素反応液をpH2から5にすることで未反応タンパク質を沈降させ、酸性水溶液可溶のペプチド画分と未反応タンパク質画分とを分離する工程を順次行う。また、タンパク質分解酵素での分解工程では、中性エンドペプチダーゼ、酸性エキソペプチダーゼを作用させる。【選択図】なし
