Abstract
Although a number of bioactive peptides are capable of angiotensin I-converting enzyme (ACE) inhibitory effects, little is known regarding the mechanism of peanut peptides using molecular simulation. The aim of this study was to obtain ACE inhibiting peptide from peanut protein and provide insight on the molecular mechanism of its ACE inhibiting action. Peanut peptides having ACE inhibitory activity were isolated through enzymatic hydrolysis and ultrafiltration. Further chromatographic fractionation was conducted to isolate a more potent peanut peptide and its antihypertensive activity was analyzed through in vitro ACE inhibitory tests and in vivo animal experiments. MALDI-TOF/TOF-MS was used to identify its amino acid sequence. Mechanism of ACE inhibition of P8 was analyzed using molecular docking and molecular dynamics simulation. A peanut peptide (P8) having Lys-Leu-Tyr-Met-Arg-Pro amino acid sequence was obtained which had the highest ACE inhibiting activity of 85.77% (half maximal inhibitory concentration (IC50): 0.0052 mg/ml). This peanut peptide is a competitive inhibitor and show significant short term (12 h) and long term (28 days) antihypertensive activity. Dynamic tests illustrated that P8 can be successfully docked into the active pocket of ACE and can be combined with several amino acid residues. Hydrogen bond, electrostatic bond and Pi-bond were found to be the three main interaction contributing to the structural stability of ACE-peptide complex. In addition, zinc atom could form metal-carboxylic coordination bond with Tyr, Met residues of P8, resulting into its high ACE inhibiting activity. Our finding indicated that the peanut peptide (P8) having a Lys-Leu-Tyr-Met-Arg-Pro amino acid sequence can be a promising candidate for functional foods and prescription drug aimed at control of hypertension.
Highlights
Peanut (Arachis hypogaea) is widely planted, harvested and consumed crop around the world
Short-term antihypertensive activity: Peanut peptide or captopril was dissolved in 1 ml normal saline according to the dosage of each group while blank control group only contained a gavage of normal saline with same volume
It has been reported that the hydrolysates produced by alcalase from food proteins showed potent antioxidant activity [41] and angiotensin I-converting enzyme (ACE) inhibiting activities [42,43]
Summary
Peanut (Arachis hypogaea) is widely planted, harvested and consumed crop around the world. As oil and protein are major constituents in peanut, it is a valuable food material in developing countries for managing malnutrition [1]. The oil extracted peanut meal is still nutritionally valuable due to its high protein content (47–55%). Peanut proteins and peptides are known for high level of L-arginine, antiatherogenic in nature and low anti-nutritional factors [4,5,6]. Because of these reasons, studies on isolation and characterization of peptides from peanut are drawing attention
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