High blood pressure or hypertension is a common chronic medical condition and a major risk factor in developing cardiovascular disease. It can also put an individual at risk for stroke, heart failure, kidney failure and other medical problems. The angiotensin-I-converting enzyme (ACE) plays a critical role in controlling blood pressure, converting the hormone angiotensin I to the potent vasoconstrictor angiotensin II as well as catalysing the degradation of the vasodilator bradykinin, both actions raising blood pressure. Therefore, ACE inhibitors are a class of medication currently in use for the treatment of hypertension. Currently synthetic ACE inhibitors are widely used, unfortunately these drugs have several negative side effects. Finding safe ACE inhibitor alternatives in natural foods has become a focus, and to date thousands of ACE-1 inhibitory peptides have been reported. These peptides have minimal toxicity or side effects when compared to their synthetic counterparts, making them an appealing alternative for the treatment of hypertension. In this study, researchers used the marine organisms, Takifugu flavidus, also known as tawny puffer, to reveal a novel ACE inhibitory peptide. Acalase and pepsin were used to hydrolyze the skin of T. flavidus and ACE-inhibitory peptides were purified and identified using ultra filtration, Sephadex G15 gel chromatography, and reverse-phase high performance liquid chromatography (RP-HPLC) with tandem mass spectrometry (LC-MS/MS). Their research uncovered a novel ACE-inhibitory peptide PPLLFAAL (Pro-Pro-Leu-Leu-Phe-Ala-Ala-Leu), which displayed high inhibitory activity with an IC50 value of 28mmol.L-1. The researchers went on to show that the through simulation models that the peptide PPLLFAAL could bind and form a stable ACE-peptide complex. Moreover, this novel peptide was shown to significantly decrease the systolic blood pressure (SBP) and diastolic blood pressure (DBP) in spontaneously hypertensive rats following intravenous administrations of the peptide. Taken together this study identified a novel peptide, PPLLFAAL, as a potential antihypertensive candidate that could be used in functional food or pharmaceuticals.
How was PEAKS used?
To identify the potential ACE-inhibitory peptide, the most active subfraction was analysed using LC-MS/MS and peptides were identified using PEAKS Studio software. The results of the search revealed the amino acid sequence of the purified peptide. In determining the sequence of the inhibitory peptides, the researchers were able to synthesise and further test the efficacy of PPLLFAAL as an ACE-inhibitory peptide.
Su Y, Chen S, Cai S, Liu S, Pan N, Su J, Qiao K, Xu Min, Chen B, Yang S and Liu Z. (2021) A Novel Angiotensin-I-Converting Enzyme (ACE) Inhibitory Peptide from Takifugu flavidus. Mar. Drugs. 19 (12):651. doi:10.3390/md19120651. PMID: 34940650. PMCID: PMC8705986.
Alcalase, neutral protease, and pepsin were used to hydrolyze the skin of Takifugu flavidus. The T. flavidus hydrolysates (TFHs) with the maximum degree of hydrolysis (DH) and angiotensin-I-converting enzyme (ACE)-inhibitory activity were selected and then ultra-filtered to obtain fractions with components of different molecular weights (MWs) (<1, 1–3, 3–10, 10–50, and >50 kDa). The components with MWs < 1 kDa showed the strongest ACE-inhibitory activity with a half-maximal inhibitory concentration (IC50) of 0.58 mg/mL. Purification and identification using semi-preparative liquid chromatography, Sephadex G-15 gel chromatography, RP-HPLC, and LC–MS/MS yielded one new potential ACE-inhibitory peptide, PPLLFAAL (non-competitive suppression mode; IC50 of 28 μmmol·L−1). Molecular docking and molecular dynamics simulations indicated that the peptides should bind well to ACE and interact with amino acid residues and the zinc ion at the ACE active site. Furthermore, a short-term assay of antihypertensive activity in spontaneously hypertensive rats (SHRs) revealed that PPLLFAAL could significantly decrease the systolic blood pressure (SBP) and diastolic blood pressure (DBP) of SHRs after intravenous administration. These results suggested that PPLLFAAL may have potential applications in functional foods or pharmaceuticals as an antihypertensive agent.