Ibrahim Hisham R, Ahmed Ahmed S, Miyata Takeshi
Department of Biochemistry and Biotechnology, Faculty of Agriculture, Kagoshima University, Kagoshima 890-0065, Japan.
Department of Food Hygiene and Control, Faculty of Veterinary Medicine, South Valley University, Qena 83523, Egypt.
J Adv Res. 2017 Jan;8(1):63-71. doi: 10.1016/j.jare.2016.12.002. Epub 2016 Dec 18.
Angiotensin-converting enzyme (ACE) plays a central role in blood pressure regulation by producing the vasoconstrictor angiotensin II. The inhibition of ACE with natural inhibitors, as alternatives to avoid the side effect of synthetic drugs, is a major target in the prevention of hypertension. In this study, we examined the separated caseins and whey proteins of goat milk for the presence of ACE inhibitory peptides. Digestion of isolated whey proteins and caseins of goat milk by gastric pepsin generated soluble hydrolysates exhibiting significant inhibition of ACE compared to weak inhibition by undigested proteins. The hydrolysates were fractionated by size exclusion chromatography, Sephacryl S-100 column, into four fractions (F1-F4). The late-eluting fraction (F4) of either whey or caseins exhibited greater ACE inhibition. Peptides in both F4 fractions, isolated by RP-HPLC, exhibited variable ACE inhibitory activities with the hydrophobic peptide peaks being the most potent ACE inhibitors. MALDI-TOF MS/MS resulted in identification of three potent ACE inhibitory peptides: PEQSLACQCL from β-lactoglobulin (residues 113-122), QSLVYPFTGPI from β-casein (residues 56-66), and ARHPHPHLSFM from κ-casein (residues 96-106). The peptides from whey and caseins exert significant ACE inhibitory activities comparable to that of captopril, an antihypertensive drug, exhibiting IC50 values of 4.45 μM and 4.27 μM, respectively. The results introduce, for the first time, new potent ACE-inhibitory peptides that can be released by gastric pepsin of goat milk whey and caseins and thus may pave the way for their candidacy as anti-hypertensive bioactive peptides and prevention of associated disorders.
血管紧张素转换酶（ACE）通过产生血管收缩剂血管紧张素II在血压调节中起核心作用。用天然抑制剂抑制ACE作为避免合成药物副作用的替代方法，是预防高血压的主要目标。在本研究中，我们检测了山羊奶中的分离酪蛋白和乳清蛋白是否存在ACE抑制肽。与未消化蛋白质的微弱抑制相比，用胃蛋白酶消化山羊奶分离的乳清蛋白和酪蛋白产生的可溶性水解产物对ACE有显著抑制作用。通过尺寸排阻色谱法，用Sephacryl S-100柱将水解产物分离成四个级分（F1-F4）。乳清或酪蛋白的后期洗脱级分（F4）表现出更大的ACE抑制作用。通过反相高效液相色谱法分离的两个F4级分中的肽表现出不同的ACE抑制活性，其中疏水肽峰是最有效的ACE抑制剂。基质辅助激光解吸电离飞行时间串联质谱（MALDI-TOF MS/MS）鉴定出三种有效的ACE抑制肽：来自β-乳球蛋白的PEQSLACQCL（第113-122位氨基酸残基）、来自β-酪蛋白的QSLVYPFTGPI（第56-66位氨基酸残基）和来自κ-酪蛋白的ARHPHPHLSFM（第96-106位氨基酸残基）。来自乳清和酪蛋白的肽发挥的ACE抑制活性与抗高血压药物卡托普利相当，IC50值分别为4.45 μM和4.27 μM。这些结果首次引入了可由山羊奶乳清和酪蛋白的胃蛋白酶释放的新型强效ACE抑制肽，从而可能为它们作为抗高血压生物活性肽及预防相关疾病的候选物铺平道路。
