Chen Yu, Zhang Yu, Qi Qianhui, Liang Feng, Wang Nan, Chen Qihe, Li Xue, Sun Suling, Wang Xinquan, Bai Kaiwen, Wang Wei, Jiao Yingchun
College of Agriculture and Animal Husbandry, Qinghai University, Xining, China.
Institute of Agricultural Safety and Nutrition, Zhejiang Academy of Agricultural Sciences, Hangzhou, China.
Front Nutr. 2023 Feb 7;9:1064526. doi: 10.3389/fnut.2022.1064526. eCollection 2022.
Angiotensin-I converting enzyme (ACE) inhibitory peptides drew wide attention in the food industry because of their natural reliability, non-toxicity, and safety. However, the characteristics of ACE inhibitory peptides obtained from protein hydrolysate of mulberry leaf prepared by Flavourzyme were still unclear. Based on the single-factor test, the Plackett-Burman test and response surface test were used to determine the key factors affecting the ACE inhibition rate in mulberry leaf protein hydrolysate and the optimum conditions of enzymatic hydrolysis. The results showed that the optimum technical parameters were as follows: the ratio of material to liquid is 1: 25 (w / v, g/mL), the Flavourzyme to substrate ratio was 3,000 U/g, the temperature of enzymatic hydrolysis was 50°C, pH was 6.3, and the time of enzymatic hydrolysis was 2.9 h. The ACE inhibitory peptides in the mulberry leaf protein hydrolysates were purified by ultrafiltration and gel filtration, aiming to obtain the highest active component. The 12 peptide sequences were identified by reverse liquid chromatography-mass spectrometry, and then, they were docked to the crystal structure of human angiotensin-I converting enzyme (1O8A), and the interaction mechanisms of 12 peptide sequences and 1O8A were analyzed. The docking results showed that among the 12 peptide sequences, ERFNVE (792.37 Da), TELVLK (351.72 Da), MELVLK (366.72 Da), and FDDKLD (376.67 Da), all had the lowest docking energy, and inhibition constant. The chemosynthetic ERFNVE (IC: 2.65 mg/mL), TELVLK (IC: 0.98 mg/mL), MELVLK (IC:1.90 mg/mL) and FDDKLD (IC:0.70 mg/mL) demonstrated high ACE-inhibitory activity with competitive inhibition mode. These results indicated that the ACE-inhibiting peptides from mulberry leaf protein hydrolyzed (FHMP) had the potential activities to inhibit ACE and could be used as functional food or drugs to inhibit ACE. This work provides positive support for mining the biological activity of mulberry leaves in the treatment of hypertension.
血管紧张素转换酶（ACE）抑制肽因其天然可靠性、无毒性和安全性而在食品工业中备受关注。然而，由风味酶制备的桑叶蛋白水解物中获得的ACE抑制肽的特性仍不清楚。基于单因素试验，采用Plackett-Burman试验和响应面试验来确定影响桑叶蛋白水解物中ACE抑制率的关键因素以及酶解的最佳条件。结果表明，最佳工艺参数如下：料液比为1:25（w/v，g/mL），风味酶与底物的比例为3000 U/g，酶解温度为50℃，pH为6.3，酶解时间为2.9 h。通过超滤和凝胶过滤对桑叶蛋白水解物中的ACE抑制肽进行纯化，旨在获得活性最高的成分。通过反相液相色谱-质谱法鉴定了12个肽序列，然后将它们对接至人血管紧张素转换酶（1O8A）的晶体结构，并分析了12个肽序列与1O8A的相互作用机制。对接结果表明，在12个肽序列中，ERFNVE（792.37 Da）、TELVLK（351.72 Da）、MELVLK（366.72 Da）和FDDKLD（376.67 Da）的对接能量和抑制常数均最低。化学合成的ERFNVE（IC：2.65 mg/mL）、TELVLK（IC：0.98 mg/mL）、MELVLK（IC：1.90 mg/mL）和FDDKLD（IC：0.70 mg/mL）表现出高ACE抑制活性，呈竞争性抑制模式。这些结果表明，桑叶蛋白水解物中的ACE抑制肽具有抑制ACE的潜在活性，可作为功能性食品或药物用于抑制ACE。这项工作为挖掘桑叶在治疗高血压方面的生物活性提供了积极支持。
