In vitro and in vivo ACE inhibitory of pistachio hydrolysates and in silico mechanism of identified peptide binding with ACE

Dual-function activity prediction of fingered citron: Integrating hypotensive and Hypolipidaemic effects via molecular docking and QSAR methods

For the further research of peptides with hypotensive and hypolipidaemic capacities. This study highlighted the both capacities of Fingered Citron Hydrolysates (FCH). In vitro results shown FCH inhibited ACE activity (slope: -0.11), exhibited pancreatic lipase inhibitory capacity (slope: 22.53), and cholesterol esterase inhibitory capacity (63.25 % at 30 mg/mL). The peptides APPDPIL, DAPIFH, NIPVIGF, and QIPGLN exhibited both these capacities. Active screening and in silico simulations were used for discovery and validation. Notably, in silico simulations validated our hypotheses, with Quantitative Structure-Activity Relationship (QSAR) models used to predict the values of hypotensive and hypolipidaemic peptides; molecular docking confirmed the interaction modes. Additionally, this study discusses the active sites and characteristics of hypotensive and hypolipidaemic peptides. The workflow in this study may also provide a viable approach for research on dual-and multifunctional peptides.

A highly active angiotensin I-converting enzyme inhibitory peptide KAKW designed based on the role of C-terminal residue, and its antihypertensive effects on spontaneously hypertensive rats

Angiotensin converting enzyme (ACE) inhibitory peptide KAKP with IC50 of 7.23 ± 0.30 μM was identified from trypsin hydrolysate of pistachio (Pistacia vera L.) through multiple purifications. A series of peptides were designed based on KAKP to reveal the role of the C-terminal residue in the ACE inhibition, including KAK-Xaa (hydrophobic residue), KAK and KAPK. The designed peptide KAKW exhibited a superior ACE inhibitory effect with IC50 of 2.02 ± 0.20 μM. Molecular docking discovered that the hydrophobic C-terminal residues with ring structure facilitated the interaction with Zn2+ and π-π interactions within the ACE active pocket. Isothermal titration calorimetry revealed that the thermodynamic property of KAKW was enthalpy-driven with a lower Kd (57.7 nM) than KAKP (141 nM). KAKW could decrease 20 mmHg SBP at 4 h and 18 mmHg DBP at 6 h during the acute trial of spontaneously hypertensive rats (SHRs), compared to that Lisinopril dropped 33 mmHg SBP and 28 mmHg DBP at 2 h. After a subacute administration of KAKW for 4 w, the strong inhibition of 61.6 % serum ACE activity and the reduction of 33.3 % angiotensin Ⅱ level were achieved. Although KAKW was less potent than Lisinopril, it provided a more moderate and sustained reduction in blood pressure, beneficial for long-term hypertension management. Meanwhile, KAKW ameliorated gut microbiota dysbiosis in SHRs and increased the levels of fecal short-chain fatty acids, demonstrating advantages over Lisinopril in modulating gut microbiota. This work provides a novel scheme for structure-activity study and a prospective candidate for hypertension management.

Screening of Oral Potential Angiotensin-Converting Enzyme Inhibitory Peptides from Zizyphus jujuba Proteins Based on Gastrointestinal Digestion In Vivo

Plant proteins are a good source of active peptides, which can exert physiological effects on the body. Predicting the possible activity of plant proteins and obtaining active peptides with oral potential are challenging. In this study, the potential activity of peptides from Zizyphus jujuba proteins after in silico simulated gastrointestinal digestion was predicted using the BIOPEP-UWM™ database. The ACE-inhibitory activity needs to be further investigated. The actual peptides in mouse intestines after the oral administration of Zizyphus jujuba protein were collected and analyzed, 113 Zizyphus jujuba peptides were identified, and 3D-QSAR models of the ACE-inhibitory activity were created and validated using a training set (34 peptides) and a test set (12 peptides). Three peptides, RLPHV, TVKPGL and KALVAP, were screened using the 3D-QSAR model and were found to bind to the active sites of the ACE enzyme, and their IC50 values were determined. Their values were 6.01, 3.81, and 17.06 μM, respectively. The in vitro digestion stabilities of the RLPHV, TVKPGL, and KALVAP peptides were 82%, 90%, and 78%. This article provides an integrated method for studying bioactive peptides derived from plant proteins.

Identification and In Silico Analysis of ACE-Inhibitory Peptides Derived from Milk Fermented by Lacticaseibacillus paracasei

Inhibition of angiotensin I-converting enzyme (ACE) activity is an effective way to treat hypertension. In the present study, the ability to produce ACE-inhibitory peptides during fermentation of skimmed milk by the Lacticaseibacillus paracasei M3 strain was evaluated, and the inhibitory mechanism and stability were studied by bioinformatics analysis. The results showed that the ACE inhibition activity of fermented milk was 71.94 ± 1.39%. After digestion with gastric juice and pancreatic juice, the ACE inhibitory activities of the fermented milk were 78.40 ± 1.93 and 74.96 ± 1.73%, respectively. After the fermented milk was purified using ultrafiltration and gel chromatography, 11 peptides from milk proteins were identified and sequenced by Nano LC-MS/MS. Molecular docking displayed that peptide PWIQPK had a high affinity, with ACE showing a binding energy of -6.10 kcal/mol. Hydrogen bonds were formed between PWIQPK and Glu384 in the S1 active pocket of ACE and Asp358. In addition, van der Waals forces were observed. In silico proteolysis suggested that PWIQPK could resist the digestion of pepsin and trypsin, indicating that it is relatively stable in the digestive tract. All results indicate that milk fermented by L. paracasei M3 has the potential to be used as a functional food having antihypertensive effects.

ACE inhibitory activity and salt-reduction properties of umami peptides from chicken soup

Angiotensin-I-converting enzyme (ACE) inhibitory activity and salt-reduction properties of umami peptides identified in chicken soup were investigated. The ACE inhibition rate of TPLVDR (91.22%) and AEINKILGN (81.26%) was significantly higher than other umami peptides, and their semi-inhibitory concentration was 0.017 mM and 0.034 mM, respectively. After in vitro digestion, the inhibitory activity of AEINKILGN and TPLVDR decreased, but the original sequences were still detected. The docking results showed that AEINKILGN and TPLVDR mainly interacted with Zn²⁺ and key sites (His353, Lys511and Glu411) in the active pockets of ACE through hydrogen bonds, which was crucial to the ACE inhibitory activity. Based on response surface methodology and sensory analysis, saltiness and palatability models were established to investigate the salt-reduction effect. The optimal level of AEINKILGN was about 1.16 mg/mL in 0.44% salt solution. And the TPLVDR was applicable to the low salt solution (0.1-0.2%) at a concentration from 0.23 to 0.29 mg/mL.

Valorization of Salmo salar Skin Waste for the Synthesis of Angiotensin Converting Enzyme-1 (ACE1) Inhibitory Peptides

One of potential inhibitors which is widely used for the clinical treatment of COVID-19 in comorbid patients is Angiostensin Converting Enzyme-1 (ACE1) inhibitor. A safer peptide-based ACE1 inhibitor derived from salmon skin collagen, that is considered as the by-product of the fish processing industry have been investigated in this study. The inhibitory activity against ACE1 was examined using in vitro and in silico methods. In vitro analysis includes the extraction of acid-soluble collagen, characterization using FTIR, Raman, UV-Vis, XRD, cytotoxicity assay, and determination of inhibition against ACE1. In silico method visualizes binding affinity, molecular interaction, and inhibition type of intact collagen and active peptides derived from collagen against ACE1 using molecular docking. The results of FTIR spectra detected amide functional groups (A, B, I, II, III) and imine proline/hydroxyproline, while the results of Raman displayed peak absorption of amide I, amide III, proline/hydroxyproline ring, phenylalanine, and protein backbone. Furthermore, UV-Vis spectra showed typical collagen absorption at 230 nm and based on XRD data, the chain types in the samples were α-helix. ACE1 inhibition activity was obtained in a concentration-dependent manner where the highest was 82.83% and 85.84% at concentrations of 1000, and 2000 µg/mL, respectively, and showed very low cytotoxicity at the concentration less than 1000 µg/mL. In silico study showed an interaction between ACE1 and collagen outside the active site with the affinity of - 213.89 kcal/mol. Furthermore, the active peptides of collagen displayed greater affinity compared to lisinopril, namely HF (His-Phe), WYT (Trp-Tyr-Thr), and WF (Trp-Phe) of - 11.52; - 10.22; - 9.58 kcal/mol, respectively. The salmon skin-derived collagen demonstrated ACE1 inhibition activity with a non-competitive inhibition mechanism. In contrast, the active peptides were predicted as potent competitive inhibitors against ACE1. This study indicated that valorization of fish by-product can lead to the production of a promising bioactive compound to treat COVID-19 patient with diabetic comorbid.

Graphical Abstract

Novel antihypertensive peptides from lupin protein hydrolysate: An in-silico identification and molecular docking studies

Application of non-thermal treatment to proteins prior to enzymatic hydrolysis can facilitate the release of novel bioactive peptides (BPs) with unique biological activities. In this study, lupin protein isolate was pre-treated with ultrasound and hydrolysed using alcalase and flavourzyme to produce alcalase hydrolysate (ACT) and flavourzyme hydrolysate(FCT). These hydrolysates were fractionated into 1, 5, and 10 kDa molecular weight fractions using a membrane ultrafiltration technique. The in vitro angiotensin-converting enzyme (ACE) studies revealed that unfractionated ACT (IC₅₀ = 3.21 mg mL^-1) and FCT (IC₅₀ = 3.32 mg mL^-1) were more active inhibitors of ACE in comparison to their ultrafiltrated fractions with IC₅₀ values ranging from 6.09 to 7.45 mg mL^-1. Molecular docking analysis predicted three unique peptides from ACT (AIPPGIPY, SVPGCT, and QGAGG) and FCT (AIPINNPGKL, SGNQGP, and PPGIP) as potential ACE inhibitors. Thus, unique BPs with ACE inhibitory effects might be generated from ultrasonicated lupin protein.

In-depth peptidomic profile and molecular simulation studies on ACE-inhibitory peptides derived from probiotic fermented milk of different farm animals

Investigations into ACE inhibitory properties of probiotic fermented bovine, camel, goat, and sheep milk were performed and studied for two weeks of refrigerated storage. Results from the degree of proteolysis suggested higher susceptibility of goat milk proteins, followed by sheep and camel milk proteins, to the probiotic-mediated proteolysis. ACE-inhibitory properties displayed continuous decline in ACE-IC₅₀ values for two weeks of refrigerated storage. Overall, goat milk fermented with Pediococcus pentosaceus caused maximum ACE inhibition (IC₅₀: 262.7 µg/mL protein equivalent), followed by camel milk (IC₅₀: 290.9 µg/mL protein equivalent). Studies related to peptide identification and in silico analysis using HPEPDOCK score revealed presence of 11, 13, 9 and 9 peptides in fermented bovine, goat, sheep, and camel milk, respectively, with potent antihypertensive potential. The results obtained suggest that the goat and camel milk proteins demonstrated higher potential for generating antihypertensive peptides via fermentation when compared to bovine and sheep milk.

Identification of a novel hypotensive peptide from porcine plasma hydrolysate by in vitro digestion and rat model

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Porcine plasma was enzymatically hydrolyzed with different times.

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The hydrolysate with high hydrolysis degree was isolated and purified by G-15 gel chromatography and HPLC.

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The ace inhibition rates of different purified compounds were determined.

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The sequence of the polypeptide with best ace inhibition (IFPPKPKDTL) was determined by Q exactive LC-MS / MS.

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The hypotensive function of synthetic peptide IFPPKPKDTL was also determined in spontaneously hypertensive rat.

We separated a novel functional peptide IFPPKPKDTL from porcine plasma hydrolysate by chromatography, HPLC, and identified by Q Exactive LC-MS/MS. Results showed that IFPPKPKDTL had a significant ability of ACE inhibition (76.6%) likely due to the presence of hydrophobic, aromatic, and acidic amino acids that can inactivate ACE by binding Zn²⁺, providing a hydrogen atom to maintain the link between ACE and the peptide. Furthermore, the ACE inhibition of synthetic IFPPKPKDTL was improved by 15.6% after in vitro digestion. Additionally, the systolic blood pressure and diastolic blood pressure of spontaneously hypertensive rats gavaged by the peptide (30 mg/kg). Thereby, ACE inhibitory peptide IFPPKPKDTL from porcine plasma was stable and has potential functional value.

Quantitative In Silico Evaluation of Allergenic Proteins from Anacardium occidentale, Carya illinoinensis, Juglans regia and Pistacia vera and Their Epitopes as Precursors of Bioactive Peptides

The aim of the study presented here was to determine if there is a correlation between the presence of specific protein domains within tree nut allergens or tree nut allergen epitopes and the frequency of bioactive fragments and the predicted susceptibility to enzymatic digestion in allergenic proteins from tree nuts of cashew (Anacardium occidentale), pecan (Carya illinoinensis), English walnut (Juglans regia) and pistachio (Pistacia vera) plants. These bioactive peptides are distributed along the length of the protein and are not enriched in IgE epitope sequences. Classification of proteins as bioactive peptide precursors based on the presence of specific protein domains may be a promising approach. Proteins possessing a vicilin, N-terminal family domain, or napin domain contain a relatively low occurrence of bioactive fragments. In contrast, proteins possessing the cupin 1 domain without the vicilin N-terminal family domain contain a relatively high total frequency of bioactive fragments and predicted release of bioactive fragments by the joint action of pepsin, trypsin, and chymotrypsin. This approach could be utilized in food science to simplify the selection of protein domains enriched for bioactive peptides.

Computational and pharmacokinetics studies of 1,3-dimethylbenzimidazolinone analogues of new proposed agent against Alzheimer's disease

Background

Alzheimer's disease (AD) is a multifactorial disorder that gradually destroys wisdom and memory skills. Currently, this disease can only be treated palliatively. However, the molecular mechanisms underlying this condition remain elusive. Therefore, these treatments are inadequate. Current medications can only increase patient warning signs. Chemical structures were drawn using Chemsketch software. Spartan’14 software was used to optimize the structures using density functional theory (DFT). The PaDEL software was used to generate the descriptors. The genetic function algorithm (GFA) and multi-linear regression (MLR) approaches were used to generate the QSAR model.

Results

In the present study, we performed a computational investigation, molecular docking, and pharmacokinetics analysis of 1,3-dimethylbenzimidazolinone derivatives. The descriptors generated in the model are AATS7i, MATS5p, SpMin7_Bhe, and GATS6c. Compounds 13 and 21 have the best binding scores, 11.2 kcal/mol and 10.8 kcal/mol, respectively, and optimal protein–ligand interactions with AChE. These compounds have brilliant pharmacokinetic and physicochemical properties.

Conclusions

The model was validated and found to have good internal and external assessment parameters: R2 = 0.937, $$R_{{{\text{adj}}}}^{2}$$ R adj 2  = 0.863, $$Q_{{{\text{cv}}}}^{2}$$ Q cv 2  = 0.788, $$R_{{{\text{test}}}}^{2}$$ R test 2  = 0.756, LOF = 0.0268, $$cR_{{\text{p}}}^{2}$$ c R p 2  = 0.677. In summary, these data suggested that compounds 13 and 21 are promising multifunctional agents against AD.

An exploration of ACE inhibitory peptides derived from gastrointestinal protease hydrolysate of milk using a modified bioassay-guided fractionation approach coupled with in silico analysis

An improved bioassay-guided fractionation was performed to effectively screen angiotensin-I converting enzyme inhibitory (ACEI) peptides from milk protein hydrolysate. The aqueous normal phase liquid chromatography, namely hydrophilic interaction liquid chromatography (HILIC), was used as a format of solid-phase extraction (SPE) short column for the first fractionation, then the HILIC-SPE fraction with the best ACEI activity (IC₅₀ = 61.75 ± 5.74 µg/mL; IC₅₀ = half-maximal inhibitory concentration) was obtained when eluted by 95% acetonitrile + 0.1% formic acid (fraction F1). The best HILIC-SPE fraction was further fractionated using reversed-phase (RP)-SPE short column. The best RP-SPE fraction was obtained when eluted by 20% acetonitrile + 0.1% formic acid (fraction P3) with an ACEI activity of IC₅₀ 36.22 ± 1.18 µg/mL. After the 2-step fractionation, the IC₅₀ value of fraction P3 significantly decreased by 8.92-fold when compared with the crude hydrolysate. Several peptides were identified from fraction P3 using liquid chromatography-tandem mass spectrometry. The in silico analysis of these identified sequences based on the BIOPEP database predicted that HLPLPLL (HL-7) was the most active peptide against angiotensin-converting enzyme (ACE). The HL-7 derived from β-casein showed a potent ACEI activity (IC₅₀ value is 16.87 ± 0.3 µM). The contents of HL-7 in the gastrointestinal protease hydrolysate and RP-SPE fraction originated from 1 mg of milk proteins were quantified using a multiple reaction monitoring mode upon liquid chromatography-tandem mass spectrometry analysis to give 19.86 ± 1.14 pg and 14,545.8 ± 572.9 pg, respectively. Besides, the kinetic study indicated that HL-7 was a competitive inhibitor and the result was rationalized using the docking simulation. The study demonstrated an efficient screening of ACEI peptides from commercially available milk powders using a simple SPE process instead of a sophisticated instrument such as HPLC. Moreover, the potent ACEI peptide HL-7 uncovered by this method could be a natural ACE inhibitor.

Characterization of a Novel Aspartic Protease from Rhizomucor miehei Expressed in Aspergillus niger and Its Application in Production of ACE-Inhibitory Peptides

Rhizomucor miehei is an important fungus that produces aspartic proteases suitable for cheese processing. In this study, a novel aspartic protease gene (RmproB) was cloned from R. miehei CAU432 and expressed in Aspergillus niger. The amino acid sequence of RmproB shared the highest identity of 58.2% with the saccharopepsin PEP4 from Saccharomyces cerevisiae. High protease activity of 1242.2 U/mL was obtained through high density fermentation in 5 L fermentor. RmproB showed the optimal activity at pH 2.5 and 40 °C, respectively. It was stable within pH 1.5-6.5 and up to 45 °C. RmproB exhibited broad substrate specificity and had K_m values of 3.16, 5.88, 5.43, and 1.56 mg/mL for casein, hemoglobin, myoglobin, and bovine serum albumin, respectively. RmproB also showed remarkable milk-clotting activity of 3894.1 SU/mg and identified the cleavage of Lys21-Ile22, Leu32-Ser33, Lys63-Pro64, Leu79-Ser80, Phe105-Met106, and Asp148-Ser149 bonds in κ-casein. Moreover, duck hemoglobin was hydrolyzed by RmproB to prepare angiotensin-I-converting enzyme (ACE) inhibitory peptides with high ACE-inhibitory activity (IC₅₀ of 0.195 mg/mL). The duck hemoglobin peptides were further produced at kilo-scale with a yield of 62.5%. High-level expression and favorable biochemical characterization of RmproB make it a promising candidate for cheese processing and production of ACE-inhibitory peptides.

A state-of-art review on camel milk proteins as an emerging source of bioactive peptides with diverse nutraceutical properties

The generation of camel milk derived bioactive peptides (CM-BAPs) have started to grab keen interest of many researchers during the past decade. CM-BAPs have shown more significant bioactive properties in comparison to camel milk intact proteins. CM-BAPs can be obtained using enzyme hydrolysis to form hydrolysates, or by the fermentation process. In this systematic review, 46 research articles exploring the health-related bioactive properties of CM-BAPs through in-vitro and in-vivo studies have been included. CM-BAPs have been reported for their antioxidant, anti-diabetic, anti-obesity, antihypertensive, antibacterial, antibiofilm, anticancer, anti-inflammatory, anti-haemolytic, and anti-hyperpigmentation activities. The effects of factors such as molecular weight of peptides, type of enzyme, enzyme to substrate ratio, hydrolysis temperature and duration have been analysed. The in-vitro studies have provided enough evidence on certain aspects of the pharmacological actives of camel milk bioactive peptides. Nevertheless, the in-vivo studies are very limited, and no clinical studies on CM-BAPs have been reported.

Novel Angiotensin-I Converting Enzyme Inhibitory Peptides Isolated From Rice Wine Lees: Purification, Characterization, and Structure-Activity Relationship

The bioactive peptides that can inhibit angiotensin-I converting enzyme (ACE, EC. 3. 4.15.1) are considered as possible cures of hypertension. Food-derived angiotensin-I converting enzyme inhibitory (ACEi) peptides have gained more attention because of their reduced side effects. In this study, we reported the method for purifying ACEi peptides from the lees of traditional Chinese rice wine and evaluated the product's biochemical properties. After three steps of reversed-phase high-performance liquid chromatography (RP-HPLC), for the first time, we isolated, purified, and identified two novel peptides: LIIPQH and LIIPEH, both of which showed strong ACEi activity (IC₅₀-values of 120.10 ± 9.31 and 60.49±5.78 μg/ml, respectively). They were further categorized as mixed-type ACE inhibitors and were stable against both ACE and gastrointestinal enzymes during in vitro digestion. Together, these results suggest that the rice wine lees that produced as a by-product during rice wine production can be utilized in various fields related to functional foods and antihypertensive medicine.

Evaluating Peptides of Picrorhiza kurroa and Their Inhibitory Potential against ACE, DPP-IV, and Oxidative Stress

Picrorhiza kurroa Royle ex Benth. is a high-altitude plant having great medicinal value. However, its medicinal value at the peptide level is still unknown, which limits its utility in the development of peptide-based therapeutics. Here, we identify 65 peptides fromP. kurroa hydrolysate. Sequence analysis suggests that one novel bioactive peptide, ASGLCPEEAVPRR (BP1), has antioxidant potential and shows angiotensin-converting enzyme (ACE) and dipeptidyl peptidase-IV (DPP-IV) inhibitory activities. The molecular docking study showed that BP1 has a lower binding energy and strong affinity toward active pockets of ACE and DPP-IV, which explains its higher ACE [IC₅₀ = 59.90 ± 9.52 μg/mL (43.40 μM)] and DPP-IV [IC₅₀ = 3.04 ± 0.26 μg/mL (2.2 μM)] inhibitory activities. BP1 protects HEK293 cells from H₂O₂-induced oxidative damage by inhibiting intracellular reactive oxygen species (ROS) and malondialdehyde accumulation and activating the intrinsic antioxidant defense system. Additionally, phase-contrast microscopy studies revealed that pre-treatment of BP1 to HEK293 cells before exposure to H₂O₂ retains the normal morphology and blocks apoptosis. Furthermore, it also suppresses ROS-induced mitochondrial apoptosis via restoring the mitochondrial membrane potential (ΔΨm) and inhibiting caspase 3/7 activity. Therefore, BP1 has antioxidant potential and ACE and DPP-IV inhibitory activities that could be used for peptide-based formulation(s) in pharmaceuticals to treat diabetes, cardiovascular diseases, and other diseases associated with ROS.

Isolation and functionalities of bioactive peptides from fruits and vegetables: A reviews

Bioactive peptides have recently gained more research attention as potential therapies for the management of bodily disorders and metabolic syndromes of delicate health importance. On another note, there is a rising trend on a global scale for the consumption and adoption of fruit and vegetables for the fulfilment of dietary and health needs. Furthermore, fruits and vegetables are being more studied as base materials for the isolation of biologically functional components and accordingly, they have been investigated for their concomitant bioactive peptides. This review focuses on isolation and bio-functional properties of bioactive peptides from fruits and vegetables. This manuscript is potential in serving as a material collection for fundamental consultancy on peptides derived from fruits and vegetables, and further canvasses the necessitation for the use of these food materials as primal matter for such.

Roles of Dietary Bioactive Peptides in Redox Balance and Metabolic Disorders

Bioactive peptides (BPs) are fragments of 2-15 amino acid residues with biological properties. Dietary BPs derived from milk, egg, fish, soybean, corn, rice, quinoa, wheat, oat, potato, common bean, spirulina, and mussel are reported to possess beneficial effects on redox balance and metabolic disorders (obesity, diabetes, hypertension, and inflammatory bowel diseases (IBD)). Peptide length, sequence, and composition significantly affected the bioactive properties of dietary BPs. Numerous studies have demonstrated that various dietary protein-derived BPs exhibited biological activities through the modulation of various molecular mechanisms and signaling pathways, including Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2/antioxidant response element in oxidative stress; peroxisome proliferator-activated-γ, CCAAT/enhancer-binding protein-α, and sterol regulatory element binding protein 1 in obesity; insulin receptor substrate-1/phosphatidylinositol 3-kinase/protein kinase B and AMP-activated protein kinase in diabetes; angiotensin-converting enzyme inhibition in hypertension; and mitogen-activated protein kinase and nuclear factor-kappa B in IBD. This review focuses on the action of molecular mechanisms of dietary BPs and provides novel insights in the maintenance of redox balance and metabolic diseases of human.

Extraction optimization and screening of angiotensin-converting enzyme inhibitory peptides from Channa striatus through bioaffinity ultrafiltration coupled with LC-Orbitrap-MS/MS and molecular docking

Channa striatus is high-protein food with many health functions. This study aimed to prepare, screen and identify the angiotensin-converting enzyme inhibition peptides (ACEIPs) from C. striatus hydrolysates by response surface methodology and bioaffinity ultrafiltration coupled with LC-Orbitrap-MS/MS and molecular docking. The optimal conditions for preparing ACEIPs were hydrolysis temperature 55 °C, hydrolysis time 3 h, pH 9, solid-liquid ratio 1:20 g/mL, and enzyme addition 5%, the ACE inhibition and molecular weight distribution of obtained hydrolysate was 54.35% and 8770-160 Da, respectively. Seven novel ACEIPs were screened through the established high-throughput screening approach, among which, EYFR and LPGPGP showed the strongest ACE inhibition with the IC₅₀ value of 179.2 and 186.3 μM, respectively (P > 0.05). Molecular docking revealed that three and ten hydrogen bonds were formed between ACE and LPGPGP and EYFR, respectively, S1 and S2 were the major active pockets, but the major driving forces varied.

Activity and bioavailability of food protein-derived angiotensin-I-converting enzyme-inhibitory peptides

Angiotensin-I-converting enzyme (ACE) inhibitory peptides are able to inhibit the activity of ACE, which is the key enzymatic factor mediating systemic hypertension. ACE-inhibitory peptides can be obtained from edible proteins and have the function of antihypertension. The amino acid sequences and the secondary structures of ACE-inhibitory peptides determine the inhibitory activities and stability. The resistance of ACE-inhibitory peptides to digestive enzymes and peptidase affect their antihypertensive bioactivity in vivo. In this paper, the mechanism of ACE-inhibition, sources of the inhibitory peptides, structure-activity relationships, stability during digestion, absorption and transportation of ACE-inhibitory peptides, and consumption of ACE-inhibitory peptides are reviewed, which provide guidance to the development of new functional foods and production of antihypertensive nutraceuticals and pharmaceuticals.

Properties of Peanut (KAC431) Protein Hydrolysates and Their Impact on the Quality of Gluten-Free Rice Bread

Protein hydrolysates (PH) with a degree of hydrolysis (DH) of 5%, 10%, and 13% from two varieties of peanut were prepared using two commercial enzymes, Alcalase and Flavourzyme. The content of essential amino acids (30,290 mg/100 g) and hydrophobic amino acids (34,067 mg/100 g) of the peanut variety Kalasin 2 (KAC431) protein was higher than that of a common variety, Kalasin 1 (KAC1) (p < 0.05). The protein molecular weight distributions of the two varieties of peanut detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were similar, ranging from 15 to 75 kDa, with a major protein band at 50–75 kDa. The antioxidant and functional properties of derived PHs were influenced by DH. Although the foaming ability of protein was improved by DH5%, it was obviously decreased upon increasing DH further. The best emulsifying properties were observed in PH with DH5% (p < 0.05). The incorporation of PH with a small DH, especially when produced using Flavourzyme, had a highly positive impact on the specific volume and relative elasticity of gluten-free bread. The effect of PHs on bread quality was highly correlated with their functional properties. This study suggests that partially enzymatically modified proteins are suitable for incorporation in food products such as bread and other gluten-free products.

Structural and molecular bases of angiotensin-converting enzyme inhibition by bovine casein-derived peptides: an in silico molecular dynamics approach

The angiotensin-converting enzyme (ACE) plays a key role in blood pressure regulation process, and its inhibition is one of the main drug targets for the treatment of hypertension. Though various peptides from milk proteins are well-known for their ACE-inhibitory capacity, research devoted to understand the molecular bases of such property remain scarce, specifically for such peptides. Therefore, in this work, computational molecular docking and molecular dynamics calculations were performed to enlighten the intermolecular interactions involved in ACE inhibition by six different casein-derived peptides (FFVAPFPEVFGK, FALPQYLK, ALNEINQFYQK, YLGYLEQLLR, HQGLPQEVLNENLLR and NAVPITPTLNR). Two top ranked docking poses for each peptide (one with N- and the other C-terminal peptide extremity oriented towards the ACE active site) were selected for dynamic simulations (50 ns; GROMOS53A6 force field), and the results were correlated to in vitro ACE inhibition capacity. Two molecular features appeared to be essential for peptides to present high ACE inhibition capacity in vitro: i) to interact with the S1 active site residues (Ala354, Glu384, and Tyr523) by hydrogen bonds; ii) to interact with Zn²⁺ coordinated residues (His383, His387, and Glu411) by short-lenght hydrogen bonds, as observed in the cases of ALNEINQFYQK (IACE = 80.7%), NAVPITPTLNR (IACE = 80.7%), and FALPQYLK (IACE = 79.0%). Regardless of the temporal stability of these strong interactions, they promoted some disruption of Zn²⁺ tetrahedral coordination during the molecular dynamics trajectories, and were pointed as the main reason for the greatest ACE inhibition by these peptides. On the other hand, peptides with intermediate inhibition capacity (50% < I_ACE < 45%) interacted mainly by weaker interactions (e.g.: electrostatic and hydrophobic) with the Zn²⁺ coordinated residues, and were not able to change significantly its tetrahedral coordination structure. These findings may: i) assist the discrimination in silico of "good" and "bad" ACE-inhibitory peptides from other food sources, and/or ii) aid in designing de novo new molecules with ACE-inhibitory capacity. Communicated by Ramaswamy Sarma.

Antihypertensive Effects in Vitro and in Vivo of Novel Angiotensin-Converting Enzyme Inhibitory Peptides from Bovine Bone Gelatin Hydrolysate

In this study, we investigated the antihypertensive effects in vitro and in vivo of novel angiotensin-converting enzyme inhibitory (ACEI) peptides purified and identified from bovine bone gelatin hydrolysate (BGH). Thirteen ACEI peptides were identified from BGH, and among which, RGL-(Hyp)-GL and RGM-(Hyp)-GF exhibited high ACE inhibition with IC₅₀ values of 1.44 and 10.23 μM. Molecular docking predicted that RGM-(Hyp)-GF and ACE residues of Glu384, His513, and Lys511 formed hydrogen-bonding interactions at distances of 2.57, 2.99, and 2.42 + 3.0 Å. RGL-(Hyp)-GL formed hydrogen bonds with Lys511 and Tyr523 and generated hydrogen-bonding interactions with His387 and Glu411 in the zinc(II) complexation motif at distances of 2.74 and 3.03 + 1.93 Å. The maximal decrements in systolic blood pressure in spontaneously hypertensive rats induced by one-time gavage of RGL-(Hyp)-GL and RGM-(Hyp)-GF at 30 mg/kg were 31.3 and 38.6 mmHg. RGL-(Hyp)-GL had higher enzyme degradation resistance than that of RGM-(Hyp)-GF in vitro incubation in rat plasma, and they were sequentially degraded into pentapeptides and tetrapeptides within 2 h. Our results indicate that BGH can serve as a nutritional candidate to control blood pressure.

ACE inhibitory peptides derived from de-fatted lemon basil seeds: optimization, purification, identification, structure–activity relationship and molecular docking analysis

The study determines optimized process conditions to maximize ACE inhibitory peptide production. The two novel hexa-peptides (LGRNLPPI and GPAGPAGL) from de-fatted lemon basil seeds (DLBS) was achieved.

Angiotensin Converting Enzyme (ACE)-Peptide Interactions: Inhibition Kinetics, In Silico Molecular Docking and Stability Study of Three Novel Peptides Generated from Palm Kernel Cake Proteins

Three novel peptide sequences identified from palm kernel cake (PKC) generated protein hydrolysate including YLLLK, WAFS and GVQEGAGHYALL were used for stability study against angiotensin-converting enzyme (ACE), ACE-inhibition kinetics and molecular docking studies. Results showed that the peptides were degraded at different cleavage degrees of 94%, 67% and 97% for YLLLK, WAFS and GVQEGAGHYALL, respectively, after 3 h of incubation with ACE. YLLLK was found to be the least stable (decreased ACE-inhibitory activity) compared to WAFS and GVQEGAGHYALL (increased ACE-inhibitory activity). YLLLK showed the lowest Ki (1.51 mM) in inhibition kinetics study when compared to WAFS and GVQEGAGHYALL with Ki of 2 mM and 3.18 mM, respectively. In addition, ACE revealed the lowest Kmapp and Vmaxapp and higher catalytic efficiency (CE) in the presence of YLLLK at different concentrations, implying that the enzyme catalysis decreased and hence the inhibition mode increased. Furthermore, YLLLK showed the lowest docking score of -8.224 and seven interactions with tACE, while peptide GVQEGAGHYALL showed the higher docking score of -7.006 and five interactions with tACE.

Dipeptidyl peptidase-4 inhibitors can inhibit angiotensin converting enzyme

Angiotensin-1 converting enzyme inhibitors (ACEIs) improve insulin sensitivity. Inhibitors of dipeptidyl peptidase-4 (DPP-4) are anti-diabetic drugs with several cardio-renal effects. Both ACE and DPP-4 share common features. Thus, we tested if they could be inhibited by one inhibitor. First, in silico screening was used to investigate the ability of different DPP-4 inhibitors or ACEIs to interact with DPP-4 and ACE. The results of screening were then extrapolated into animal study. Fifty Sprague Dawley rats were randomly assigned into 5 groups treated with vehicle, captopril, enalapril, linagliptin or sitagliptin. Both low and high doses of each drug were tested. Baseline blood samples and samples at days 1, 8, 10, 14 were used to measure plasma DPP-4 and ACE activities and angiotensin II levels. Active glucagon-like peptide-1 (GLP-1) levels were measured after oral glucose challenge. All tested DPP-4 inhibitors could interact with ACE at a relatively reasonable binding energy while most of the ACEIs only interacted with DPP-4 at a predicted high inhibition constant. In rats, high dose of sitagliptin was able to inhibit ACE activity and reduce angiotensin II levels while linagliptin had only a mild effect. ACEIs did not significantly affect DPP-4 activity or prevent GLP-1 degradation. It seems that some DPP-4 inhibitors could inhibit ACE and this could partially explain the cardio-renal effects of these drugs. Further studies are required to determine if such inhibition could take place in clinical settings.

Antioxidant and angiotensin-converting enzyme (ACE) inhibitory activity of thymosin alpha-1 (Thα1) peptide

In this research, the antioxidant property of thymosin alpha-1 (Thα1) peptide was investigated through various antioxidant methods. Thα1 showed 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (IC50 = 20 µM) and its 2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging reached 45.33% at 80 µM (IC50 = 85 µM). In addition, hydroxyl and superoxide radical scavenging of Thα1 peptide exhibited a concentration-depended manner. The IC50 values of hydroxyl and superoxide radical scavenging were estimated to be 82 µM and 20 µM, respectively. The effect of Thα1 on eliminating superoxide radicals was higher (62.23%) than other antioxidant assays. Moreover, the antioxidant activity of Thα1 peptide was evaluated by measuring cellular reactive oxygen species (ROS). Results indicated that Thα1 decreased the generation of ROS level in 1321 N1 human neural asterocytoma cells. The inhibitory effect of Thα1 on angiotensin-converting enzyme (ACE) was determined. The kinetic parameters (Km and Vmax) and the inhibition pattern were examined. Based on the Lineweaver-Burk plot, Thα1 displayed a mixed inhibition pattern. The IC50 and Ki values of Thα1 were 0.8 µM and 3.33 µM, respectively. Molecular modeling suggested that Thα1 binds to ACE-domains with higher affinity binding to N-domain with the binding energy of -22.87 kcal/mol. Molecular docking indicated that Thα1 interacted with ACE enzyme (N- and C-domains) due to electrostatic, hydrophobic, and hydrogen forces. Our findings suggested that Thα1 possess a multifunctional peptide with dual antioxidant and ACE-inhibitory properties. Further researches are needed to investigate the antioxidant and anti-hypertensive effect of Thα1 both in vitro and in vivo.

Identification and Functional Mechanism of Novel Angiotensin I Converting Enzyme Inhibitory Dipeptides from Xerocomus badius Cultured in Shrimp Processing Waste Medium

ACE inhibitory dipeptides from Xerocomus badius fermented shrimp processing waste were isolated with ethanol, macroporous resin, chloroform, and Sephadex G-10 in sequence and identified by LC-MS/MS system coupled with electrospray ionization source. Molecular docking was performed for exploring the mechanism of their inhibitions. The results showed that the identified ACE inhibitory dipeptides were Cys-Cys and Cys-Arg with IC₅₀ values of 4.37 ± 0.07 and 475.95 ± 0.11 μM, respectively. The difference between ACE inhibitor potency of Cys-Cys and Cys-Arg could be explained by results of molecular docking. Cys-Cys formed crucial coordination between carboxyl oxygen and Zn(II), hydrogen bonds with residues Ala354(O), Ala356(HN), and Tyr523(OH), and a bump with the residue His387(NE2) at the active site of ACE. There was no coordination, except for 5 hydrogen bonds (at residues His353, Ala354, Glu384, Glu403, and Arg522) and a bump (Glu411) between Cys-Arg and active site of ACE. These findings highlighted that Cys-Cys could be considered as a novel potent ACE inhibitor, and coordination between its carboxyl oxygen and Zn(II) played significant role in defining its ACE inhibitor potency.

Production of antioxidant and ACE-inhibitory peptides from Kluyveromyces marxianus protein hydrolysates: Purification and molecular docking

Kluyveromyces marxianus protein hydrolysates were prepared by two different sonicated-enzymatic (trypsin and chymotrypsin) hydrolysis treatments to obtain antioxidant and ACE-inhibitory peptides. Trypsin and chymotrypsin hydrolysates obtained by 5 h, exhibited the highest antioxidant and ACE-inhibitory activities. After fractionation using ultra-filtration and reverse phase high performance liquid chromatography (RP-HPLC) techniques, two new peptides were identified. One fragment (LL-9, MW = 1180 Da) with the amino acid sequence of Leu-Pro-Glu-Ser-Val-His-Leu-Asp-Lys showed significant ACE inhibitory activity (IC₅₀ = 22.88 μM) while another peptide fragment (VL-9, MW = 1118 Da) with the amino acid sequence of Val-Leu-Ser-Thr-Ser-Phe-Pro-Pro-Lys showed the highest antioxidant and ACE inhibitory properties (IC₅₀ = 15.20 μM, 5568 μM TE/mg protein). The molecular docking studies revealed that the ACE inhibitory activities of VL-9 is due to interaction with the S2 (His513, His353, Glu281) and S’1 (Glu162) pockets of ACE and LL-9 can fit perfectly into the S1 (Thr345) and S2 (Tyr520, Lys511, Gln281) pockets of ACE.

Production, optimisation and characterisation of angiotensin converting enzyme inhibitory peptides from sea cucumber (Stichopus japonicus) gonad

The purification, characterization, and molecular docking study of a novel ACE inhibitory peptide (NAPHMR) derived from sea cucumber gonad hydrolysates.