The aim of this work is to explore angiotensin I-converting enzyme (ACE) inhibitory peptides from Chlorella vulgaris (C. vulgaris) and discover the inhibitory mechanism of the peptides. After C. vulgaris proteins were gastrointestinal digested in silico, several ACE inhibitory peptides with C-terminal tryptophan were screened. Among them, two novel noncompetitive ACE inhibitors, Thr-Thr-Trp (TTW) and Val-His-Trp (VHW), exhibited the highest inhibitory activity indicated by IC₅₀ values 0.61 ± 0.12 and 0.91 ± 0.31 μM, respectively. Both the peptides were demonstrated stable against gastrointestinal digestion and ACE hydrolysis. The peptides were administrated to spontaneously hypertensive rats (SHRs) in the dose 5 mg/kg body weight, and VHW could decrease 50 mmHg systolic blood pressure of SHRs (p < 0.05). Molecular docking displayed that both TTW and VHW formed six hydrogen bonds with active site pockets of ACE. Besides, isothermal titration calorimetry assay discovered that VHW could form more stable complex with ACE than TTW. Therefore, VHW was an excellent ACE inhibitor.

中文翻译：

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普通小球藻血管紧张素转化酶抑制肽的降压作用，分子对接研究和等温滴定量热法

这项工作的目的是探索来自小球藻（C. vulgaris）的血管紧张素I转换酶（ACE）抑制肽，并发现该肽的抑制机制。在计算机上胃肠消化了C. vulgaris蛋白后，筛选了一些具有C端色氨酸的ACE抑制肽。其中，两种新型非竞争性ACE抑制剂Thr-Thr-Trp（TTW）和Val-His-Trp（VHW）表现出最高的IC ₅₀抑制活性。值分别为0.61±0.12和0.91±0.31μM。两种肽均证明对胃肠道消化和ACE水解稳定。以自发性高血压大鼠（SHRs）的剂量将肽以5 mg / kg体重的剂量给药，VHW可以使SHRs的收缩压降低50 mmHg（p <0.05）。分子对接表明，TTW和VHW均与ACE的活性位点形成了六个氢键。此外，等温滴定量热法测定发现，VHW与ACE形成的络合物比TTW稳定。因此，VHW是出色的ACE抑制剂。