Identification of novel angiotensin I-converting enzyme (ACE) inhibitory peptides from wheat gluten hydrolysate by the protease of Pseudomonas aeruginosa

Computational exploration of naturally derived peptides inhibitory mechanisms against ACE enzyme, from interactions to structural-dynamics

Naturally derived peptides have gained significant attention because of their potential to reduce blood pressure. These peptides can be derived from various sources, including snake venom, marine organisms, cow's milk, seahorses, and plants. Investigating the underlying mechanisms of these peptides in lowering blood pressure is crucial for replacing synthetic drugs currently in use. In this regard, we conducted in silico studies, such as molecular docking, classical molecular dynamics (MD) simulations, and QM/MM simulation methods, on two naturally derived peptides (PAGPRGPA and WALKGYK) and Angiotensin II (ANGII) as the enzyme substrates for binding to sACE. The results of 500 ns MD calculations showed that the WALKGYK peptide occupies the ACE binding site, similar to the ANGII and BPPb peptides, two distinguished C-domain-specific inhibitors. Furthermore, QM/MM calculations demonstrated that no peptide bond cleavage was mediated by Zn2+ at the catalytic site of the peptides. However, during the 500 ns MD simulation, the backbone oxygens of LYS4 and GLY5 of the WALKGYK peptides were tightly coordinated to the Zn2+ ion. Free energy calculations also confirmed the higher affinity of the WALKGYK peptides for binding to sACE. In addition, structural analysis correlation showed a different pattern in PAGPRGPA compared to WALKGYK and ANGII. Despite the similarity of the peptide PAGPRGPA to typical ACE peptide inhibitors with hydrophobic ends, the electrostatic composition of the WALKGYK peptide showed a higher tendency towards ACE inhibition. Therefore, peptide residue compositions, such as WALKGYK, can be considered for designing new inhibitors with fewer side effects for sACE C-terminal inhibitors.

Production of Protein Hydrolysates Teff (Eragrostis tef) Flour with Antioxidant and Angiotensin-I-Converting Enzyme (ACE-I) Inhibitory Activity Using Pepsin and Cynara cardunculus L. Extract

In recent years, several studies have shown the antioxidant and antihypertensive potential of bioactive peptides. Thus, bioactive peptides are likely to be a valuable substance for the development of functional foods. There are a wide variety of sources of these peptides, including several cereals. Teff is an Ethiopian-rooted cereal with an interesting nutritional profile, mainly due to its high amount of protein. In this study, teff flour was subjected to a defatting process for optimizing the protein extraction. Such extraction was performed by precipitation from its isoelectric point, a crucial step that separates the protein from other components based on their charge. The protein obtained was subjected to enzymatic hydrolysis by pepsin and Cynara cardunculus L. The antihypertensive (angiotensin-I-converting enzyme -ACE-I- inhibitory activity) and antioxidant activity (2,2-diphenyl-1-picrylhydrazyl -DPPH- radical scavenging activity) of the peptides were determined. According to the IC50 values, the results obtained showed that the peptides from teff flour show promising bioactivity compared to other cereals. Furthermore, the peptides from teff flour obtained from C. cardunculus L. showed higher antioxidant activity (defatted teff flour -DTF-: 0.59 ± 0.05; protein extract -EP- : 1.04 ± 0.11) than those obtained with pepsin (DTF: 0.87 ± 0.09; EP: 1.73 ± 0.11). However, C. cardunculus L. hydrolyzate peptides showed lower inhibitory activity of ACE-I (DTF: 0.59 ± 0.07; EP: 0.61 ± 0.05) than the pepsin hydrolyzate (DTF: 0.15 ± 0.02; EP: 0.33 ± 0.05).

Emerging production techniques and potential health promoting properties of plant and animal protein-derived bioactive peptides

Bioactive peptides (BPs) are short amino acid sequences that that are known to exhibit physiological characteristics such as antioxidant, antimicrobial, antihypertensive and antidiabetic properties, suggesting that they could be exploited as functional foods in the nutraceutical industry. These BPs can be derived from a variety of food sources, including milk, meat, marine, and plant proteins. In the past decade, various methods including in silico, in vitro, and in vivo techniques have been explored to unravel underlying mechanisms of BPs. To forecast interactions between peptides and their targets, in silico methods such as BIOPEP, molecular docking and Quantitative Structure-Activity Relationship modeling have been employed. Additionally, in vitro research has examined how BPs affect enzyme activities, protein expressions, and cell cultures. In vivo studies on the contrary have appraised the impact of BPs on animal models and human subjects. Hence, in the light of recent literature, this review examines the multifaceted aspects of BPs production from milk, meat, marine, and plant proteins and their potential bioactivities. We envisage that the various concepts discussed will contribute to a better understanding of the food derived BP production, which could pave a way for their potential applications in the nutraceutical industry.

A simple tandem bioassay-guided SCX-RP SPE fractionation for efficient active peptide screening from Inca nut cake protein hydrolysate

Typically, bioactive peptides were uncovered from complex hydrolysates using sequential bioassay-guided fractionation. To increase the efficiency of bioactive peptide screening, a simple and convenient tandem bioassay-guided fractionation based on solid-phase extraction (SPE) was conducted to screen the angiotensin-I-converting enzyme (ACE) inhibitory peptides from the hydrolysate of Inca nut cake protein (INCP). The so-called SCX-RP SPE system was constructed by assembling SCX (strong cation exchange) and RP (reversed phase) SPE cartridges. Using this tandem SCX-RP SPE, the INCP digested with combined gastrointestinal protease (INCP GP) was fractionated into 30 fractions. The fraction F11 exhibited the highest ACE inhibitory activity among 30 fractions. The ACE IC50 of fraction F11 was calculated to be 6.6 ± 0.5 µg/mL. The ACEI activity of fraction F11 was stronger than the INCP GP hydrolysate (ACE IC50 of 12.7 ± 0.4 µg/mL). The tandem SCX-RP SPE fractionation reduced the number of ACE inhibitory (ACEI) peptide candidates from 127 peptides in the INCP GP hydrolysate to only ten peptides in fraction F11. Subsequently, WALPTQSW (WW-8) and WLPTKSW (WW-7) from fraction F11 were synthesized, and their ACE IC50 was determined to be 4.7 ± 0.1 and 7.9 ± 0.1 µM, respectively. The dipeptidyl peptidase-4 (DPP4) inhibitory and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities of WALPTQSW (WW-8) were also explored to give IC50 values of 131.7 ± 5.2 and 191.8 ± 7.0 µM, respectively. The molecular docking and inhibition mechanism studies indicated that WW-8 inhibited ACE and DPP4 as competitive and non-competitive inhibitors, respectively. The pre-incubation experiment of WW-8 toward ACE and DPP4 demonstrated that WW-8 was a true-inhibitor type. Additionally, the amount of WW-8 was quantified to be 5.8 ± 0.2 and 35 ± 0.4 µg per milligram hydrolysate and fraction F11, respectively. This study demonstrated tandem bioassay-guided SCX-RP SPE fractionation efficiently screened ACEI peptide derived from INCP GP hydrolysate, adding more value to Inca nut cake (a leftover of the oil industry) as a bioactive peptide precursor.

Potential of hydrolyzed wheat protein in soy-based meat analogues: Rheological, textural and functional properties

Hydrolyzed proteins, which are considered to possess significant bioactive properties such as antioxidant and high digestibility, have garnered increasing interest as food ingredients. This study investigates the feasibility of using hydrolyzed wheat gluten (HWG) and soy protein concentrate (SPC) in various ratios to create meat analogues using high-moisture extrusion technology. Results indicate that meat analogues with 40% HWG addition to SPC have a better texture and greater similarities in terms of hardness, chewiness, and toughness to chicken meat than meat analogues with 40% wheat gluten (WG) addition to SPC. Additionally, the meat analogues with HWG showed high antioxidant capacity, protein digestibility, and amino acid composition, indicating potential health benefits. These findings indicate that HWG could serve as a texture modifier to improve both the texture and nutritional content of meat analogues.

Structure-Activity Relationship of Novel ACE Inhibitory Undecapeptides from Stropharia rugosoannulata by Molecular Interactions and Activity Analyses

Undecapeptide is the central peptide molecule in the peptide base material of Stropharia rugosoannulata, and angiotensin-converting enzyme (ACE) plays a crucial role in hypertension. To fully explore the interaction mechanism and ACE-inhibitory activity of long-chain peptides from Stropharia rugosoannulata, the binding conformations of twenty-seven undecapeptides with the ACE receptor were revealed by molecule docking. The undecapeptide GQEDYDRLRPL with better receptor binding capacity and higher secondary mass spectral abundance was screened. All amino acid residues except proline in GQEDYDRLRPL interacted with the ACE receptor. GQEDYDRLRPL interfered with the receptor's overall structure, with significant fluctuations in amino acid residues 340-355, including two residues in the receptor's active pockets. The binding constants of GQEDYDRLRPL to the ACE receptors were at the μM level, with a kinetic binding constant of 9.26 × 10-7 M, which is a strong binding, and a thermodynamic binding constant of 3.06 × 10-6 M. Intermolecular interaction were exothermic, enthalpy-driven, and specific binding reactions. GQEDYDRLRPL had an IC50 value of 164.41 μmol/L in vitro and superior antihypertensive effects at low-gavage administration in vivo. Obtaining information on the interaction mechanism of ACE-inhibitory undecapeptides from S. rugosoannulata with the ACE receptor will help to develop and utilize ACE inhibitors of natural origin.

Peptidomics analysis of Jiang-Flavor Daqu from high-temperature fermentation to mature and in different preparation season

Jiang-Flavor Daqu (JFDQ) is a grain-type fermented starter for brewing Chinese liquor. Peptides, the metabolites of proteins in JFDQ, are important for the quality and flavor of JFDQ or even the liquor. The peptide variations in the progress of JFDQ preparation were investigated using RPLC-MS/MS. The JFDQ after high-temperature fermenting (HTF_SU) and after ripening (M_SU), as well as the mature JFDQ prepared in spring (M_SP) and in summer (M_SU), were compared respectively. These two groups were investigated from peptides, precursor proteins, abundance, interactions, and potential antimicrobial peptides (pAMPs). A total of 177, 158, and 262 peptides from HTF_SU, M_SP, and M_SU were identified, respectively. Significant differences (P < 0.01) in the abundance of shared peptides were found in different fermentation stage group (HTF_M), and stronger positive correlations were observed in different preparation season group (MSP_MSU). The interactions of the shared peptides in HTF_M and in MSP_MSU were investigated respectively. In addition, 8 pAMPs in HTF_SU, 5 in M_SP, and 22 in M_SU were predicted using CAMPR3, and their core functional regions were analyzed. This systematic study demonstrated the influences of fermentation stage and preparation season on the peptide profiles in JFDQ, which would provide theoretical guidance and be helpful for JFDQ production. SIGNIFICANCE: Peptidomics analysis showed that the peptide profiles of JFDQ varied in different fermentation stages and different preparation seasons, which mainly resulted from the peptides with high abundance, high interaction degrees, and potential antimicrobial activity, as well as the important precursor proteins such as glutens. This systematic study would benefit for the insufficiency of peptide research of JFDQ till now, and provide theoretical guidance for JFDQ production.

Production of enzymatic hydrolysates with in vitro antioxidant, antihypertensive, and antidiabetic properties from proteins derived from Arthrospira platensis

The microalga Arthrospira platensis BEA 005B was produced using 80 m² (9 m³) raceway photobioreactors achieving a biomass productivity of 28.2 g·m^-2·day^-1 when operating the reactors in semi-continuous mode (0.33 day^-1). The produced biomass was rich in proteins (58.1 g·100 g^-1) and carbohydrates (25.6 g·100 g^-1); the content of phycocyanins and allophycocyanins was 115.4 and 36.9 mg·g^-1, respectively. Ultrasounds and high-pressure homogenisation allowed recovering approximately 90% of the initial protein content of the biomass; however, the energetic requirements of the former (∼100 kJ·kg^-1) were significantly lower than those of high-pressure homogenisation (∼200 kJ·kg^-1). An in silico analysis revealed that papain and ficin would allow releasing a large number of bioactive peptides with antioxidant, antihypertensive (ACE-I and renin), and antidiabetic (DPP-IV, α-amylase, and α-glucosidase) properties. Both were assessed in vitro together with Alcalase and pepsin leading to the generation of enzymatic hydrolysates with in vitro bioactivity.

ACE Inhibitory Peptides Derived from Muscovy Duck (Cairina moschata) Plasma

In this study, angiotensin-converting enzyme inhibitory peptides (ACE-IPs) derived from Muscovy duck (Cairina moschata) plasma hydrolysate (MDPH) were investigated. According to the general research protocol for bioactive peptides, the crude ACE-IPs of Muscovy duck plasma were separated and purified by ultrafiltration, gel chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC). Then the components with the highest ACE inhibition potential were selected for identification. Finally, the inhibition mechanism was explored by molecular docking and in silico simulated digestion. A total of 121 peptides was detected, and five were screened for synthesis verification and molecular docking. The peptide VALSSLRP revealed high ACE inhibitory activity (91.67 ± 0.73%) because this peptide bound tightly to the S1' pocket and formed 3 hydrogen bonds. Meaningfully, this work provides some new information about the generation of ACE-IPs derived from duck blood plasma.

Novel Peptide Sequences with ACE-Inhibitory and Antioxidant Activities Derived from the Heads and Bones of Hybrid Groupers (Epinephelus lanceolatus × Epinephelus fuscoguttatus)

The heads and bones of hybrid groupers are potential precursors for angiotensin-converting enzyme (ACE)-inhibitory and antioxidant peptides. The aim of this study was to isolate the dual-action peptides from the Alcalase-treated head and bone hydrolysate of hybrid groupers followed by identification of the novel peptides. The stability of these peptides against stimulated in vitro gastrointestinal digestion (SGID) was also determined. Fraction HB-IV (less than 1 kDa) obtained from ultrafiltration showed the strongest ACE-inhibition ability (IC50: 0.28 mg/mL), which was comparable to the potency of the commercial supplement, PeptACE (IC50: 0.22 mg/mL). This fraction also demonstrated the highest hydroxyl radical scavenging and metal-chelating activities. However, further fractionation of HB-IV by a series of chromatography resulted in peptide fractions of reduced ACE-inhibitory and antioxidant activities. The hydroxyl radical scavenging and reduction potential of HB-IV were enhanced, whereas ACE-inhibitory and metal-chelating activities were reduced following SGID. A total of 145 peptide sequences were identified from HB-IV, of which 137 peptides were novel to the BIOPEP database. The results suggested that the bioactive peptides isolated from the heads and bones of hybrid groupers could be used as functional foods/ingredients with potential ACE-inhibitory and antioxidant effects.

Peptidomics-based identification of an antimicrobial peptide derived from goat milk fermented by Lactobacillus rhamnosus (C25)

Antimicrobial peptides (AMPs) are emerging as promising novel drug applicants. In the present study, goat milk was fermented using Lactobacillus rhamnosus C25 to generate bioactive peptides (BAPs). The peptide fractions generated were separated using ultrafiltration membranes with molecular weight cut-offs of 3, 5, and 10 kDa, and their antimicrobial activity toward Gram-positive and Gram-negative bacteria was investigated. Isolated AMPs were characterized using RP-HPLC and identified by LC-MS/MS. A total of 569 sequences of peptides were identified by mass spectrometry. Out of the 569, 36 were predicted as AMPs, 21 were predicted as cationic, and out of 21, 6 AMPs were helical peptides. In silico analysis indicated that the majority of peptides were antimicrobial and cationic in nature, an important factor for peptide interaction with the negative charge membrane of bacteria. The results showed that the peptides of <5 kDa exhibited maximum antibacterial activity against E. faecalis, E. coli, and S. typhi. Further, molecular docking was used to evaluate the potent MurD ligase inhibitors. On the basis of ligand binding energy, six predicted AMPs were selected and then analyzed by AutoDock tools. Among the six AMPs, peptides IGHFKLIFSLLRV (-7.5 kcal/mol) and KSFCPAPVAPPPPT (-7.6 kcal/mol), were predicted as a high-potent antimicrobial. Based on these findings, in silico investigations reveal that proteins of goat milk are a potential source of AMPs. This is for the first time that the antimicrobial peptides produced by Lactobacillus rhamnosus (C25) fermentation of goat milk have been identified via LC-MS/MS and predicted as AMPs, cationic charges, helical structure in nature, and potent MurD ligase inhibitors. These peptides can be synthesized and improved for use as antimicrobial agents. PRACTICAL APPLICATIONS: Goat milk is considered a high-quality source of milk protein. According to this study, goat milk protein is a potential source of AMPs, Fermentation can yield goat milk-derived peptides with a broad antibacterial activity spectrum at a low cost. The approach described here could be beneficial in that the significant AMPs can be synthesized and used in the pharmaceutical and food industries.

Unconventional microbial proteases as promising tools for the production of bioactive protein hydrolysates

Enzymatic hydrolysis is the most prominent strategy to release bioactive peptides from different food proteins and protein-rich by-products. Unconventional microbial proteases (UMPs) have gaining increased attention for such purposes, particularly from the 2010s. In this review, we present and discuss aspects related to UMPs production, and their use to obtain bioactive protein hydrolysates. Antioxidant and anti-hypertensive potentials, commonly evaluated through in vitro testing, are mainly reported. The in vivo bioactivities of protein hydrolysates and peptides produced through UMPs action are highlighted. In addition to bioactivities, enzymatic hydrolysis acts by modulating the functional properties of proteins for potential food uses. The compiled literature indicates that UMPs are promising biocatalysts to generate bioactive protein hydrolysates, adding up to commercially available enzymes. From the recent interest on this topic, continuous and in-depth research is needed to advance toward the applicability and commercial utility of both UMPs and obtained hydrolysates.

An Overview of the Potentialities of Antimicrobial Peptides Derived from Natural Sources

Antimicrobial peptides (AMPs) are constituents of the innate immune system in every kind of living organism. They can act by disrupting the microbial membrane or without affecting membrane stability. Interest in these small peptides stems from the fear of antibiotics and the emergence of microorganisms resistant to antibiotics. Through membrane or metabolic disruption, they defend an organism against invading bacteria, viruses, protozoa, and fungi. High efficacy and specificity, low drug interaction and toxicity, thermostability, solubility in water, and biological diversity suggest their applications in food, medicine, agriculture, animal husbandry, and aquaculture. Nanocarriers can be used to protect, deliver, and improve their bioavailability effectiveness. High cost of production could limit their use. This review summarizes the natural sources, structures, modes of action, and applications of microbial peptides in the food and pharmaceutical industries. Any restrictions on AMPs' large-scale production are also taken into consideration.

Cereals as a Source of Bioactive Compounds with Anti-Hypertensive Activity and Their Intake in Times of COVID-19

Cereals have phytochemical compounds that can diminish the incidence of chronic diseases such as hypertension. The angiotensin-converting enzyme 2 (ACE2) participates in the modulation of blood pressure and is the principal receptor of the virus SARS-CoV-2. The inhibitors of the angiotensin-converting enzyme (ACE) and the block receptors of angiotensin II regulate the expression of ACE2; thus, they could be useful in the treatment of patients infected with SARS-CoV-2. The inferior peptides from 1 to 3 kDa and the hydrophobic amino acids are the best candidates to inhibit ACE, and these compounds are present in rice, corn, wheat, oats, sorghum, and barley. In addition, the vitamins C and E, phenolic acids, and flavonoids present in cereals show a reduction in the oxidative stress involved in the pathogenesis of hypertension. The influence of ACE on hypertension and COVID-19 has turned into a primary point of control and treatment from the nutritional perspective. The objective of this work was to describe the inhibitory effect of the angiotensin-converting enzyme that the bioactive compounds present in cereals possess in order to lower blood pressure and how their consumption could be associated with reducing the virulence of COVID-19.

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.

Recent advances in bioactive peptides from cereal-derived Foodstuffs

Cereal-derived proteins account for a major part of human dietary protein consumption. Natural bioactive peptides (NBPs) from these proteins involve a variety of physiological activities and play an important role in the promotion of human health. This review focuses on the characteristics of NBPs obtained from cereals, and the commonly used methods for preparation, separation, purification, and identification. We also discussed the biological functions of cereal-derived NBPs (CNBPs), including the activities of antioxidant, immunomodulatory, antimicrobial, and regulation of hyperglycaemia and hypertension. The paper summarised the latest progress in the research and application of CNBPs and analysed the prospects for the development and application of several protein by-products, providing an important way to improve the added value of protein by-products in cereal processing.

Application of enzymes in the preparation of wheat germ polypeptides and their biological activities

Wheat germ, a byproduct of wheat industrial processing, contains 30% protein and is a comprehensive source of plant-based protein. But a large amount of wheat germs are disposed of as waste every year. Wheat germ protein can be hydrolyzed into polypeptides with antioxidant, antihypertensive, anti-tumor, bacteriostatic and other activities. At present, researches on the hydrolysis of wheat germ protein and the preparation of bioactive peptides from wheat germ protein have attracted increasing attentions. However, the traditional protein hydrolysis method, protease hydrolysis, can no longer meet the market's needs for efficient production. Various auxiliary means, such as ultrasound, microwave and membrane separation, were applied to boost the yield and biological activity of wheat germ peptides by enzymatic hydrolysis. Under ultrasound and microwave, the protein structure may expand to increase the binding sites between enzyme and substrate and promote hydrolysis efficiency. Membrane separation is applied to separate products from enzymatic hydrolysate to reduce the inhibitory effect of the product on the hydrolysis reaction. The paper reviewed the hydrolysis methods of wheat germ protein and summarized the biological activity of wheat germ peptides to provide references for further study of wheat germ peptides.

Bioactive Peptides: An Understanding from Current Screening Methodology

Bioactive peptides with high potency against numerous human disorders have been regarded as a promising therapy in disease control. These peptides could be released from various dietary protein sources through hydrolysis processing using physical conditions, chemical agents, microbial fermentation, or enzymatic digestions. Considering the diversity of the original proteins and the complexity of the multiple structural peptides that existed in the hydrolysis mixture, the screening of bioactive peptides will be a challenge task. Well-organized and well-designed methods are necessarily required to enhance the efficiency of studying the potential peptides. This article, hence, provides an overview of bioactive peptides with an emphasis on the current strategy used for screening and characterization methods. Moreover, the understanding of the biological activities of peptides, mechanism inhibitions, and the interaction of the complex of peptide–enzyme is commonly evaluated using specific in vitro assays and molecular docking analysis.

Plant-derived proteins as a sustainable source of bioactive peptides: recent research updates on emerging production methods, bioactivities, and potential application

The development of novel protein sources to compensate for the expected future shortage of traditional animal proteins due to their high carbon footprint is a major contemporary challenge in the agri-food industry currently. Therefore, both industry and consumers are placing a greater emphasis on plant proteins as a sustainable source of protein to meet the growing nutritional demand of ever increasing population. In addition to being key alternatives, many plant-based foods have biological properties that make them potentially functional or health-promoting foods, particularly physiologically active peptides and proteins accounting for most of these properties. This review discusses the importance of plant-based protein as a viable and sustainable alternative to animal proteins. The current advances in plant protein isolation and production and characterization of bioactive hydrolysates and peptides from plant proteins are described comprehensively. Furthermore, the recent research on bioactivities and bioavailability of plant protein-derived bioactive peptides is reviewed briefly. The limitations of using bioactive peptides, regulatory criteria, and the possible future applications of plant protein-derived bioactive peptides are highlighted. This review may help understand plant proteins and their bioactive peptides and provide valuable suggestions for future research and applications in the food industry.

Ensemble-AHTPpred: A Robust Ensemble Machine Learning Model Integrated With a New Composite Feature for Identifying Antihypertensive Peptides

Hypertension or elevated blood pressure is a serious medical condition that significantly increases the risks of cardiovascular disease, heart disease, diabetes, stroke, kidney disease, and other health problems, that affect people worldwide. Thus, hypertension is one of the major global causes of premature death. Regarding the prevention and treatment of hypertension with no or few side effects, antihypertensive peptides (AHTPs) obtained from natural sources might be useful as nutraceuticals. Therefore, the search for alternative/novel AHTPs in food or natural sources has received much attention, as AHTPs may be functional agents for human health. AHTPs have been observed in diverse organisms, although many of them remain underinvestigated. The identification of peptides with antihypertensive activity in the laboratory is time- and resource-consuming. Alternatively, computational methods based on robust machine learning can identify or screen potential AHTP candidates prior to experimental verification. In this paper, we propose Ensemble-AHTPpred, an ensemble machine learning algorithm composed of a random forest (RF), a support vector machine (SVM), and extreme gradient boosting (XGB), with the aim of integrating diverse heterogeneous algorithms to enhance the robustness of the final predictive model. The selected feature set includes various computed features, such as various physicochemical properties, amino acid compositions (AACs), transitions, n-grams, and secondary structure-related information; these features are able to learn more information in terms of analyzing or explaining the characteristics of the predicted peptide. In addition, the tool is integrated with a newly proposed composite feature (generated based on a logistic regression function) that combines various feature aspects to enable improved AHTP characterization. Our tool, Ensemble-AHTPpred, achieved an overall accuracy above 90% on independent test data. Additionally, the approach was applied to novel experimentally validated AHTPs, obtained from recent studies, which did not overlap with the training and test datasets, and the tool could precisely predict these AHTPs.

Optimisation and Characterisation of Novel Angiotensin-Converting Enzyme Inhibitory Peptides Prepared by Double Enzymatic Hydrolysis from Agaricus bisporus Scraps

Food-derived hypotensive peptides have attracted attention in the field of active peptide research in recent years. In this study, based on ACE inhibition rate and using the Box–Behnken central combination design principle to optimise the process of ACE inhibitor peptides prepared by double-enzyme hydrolysis. The amino acid sequences of ACE inhibitor peptides were determined by liquid chromatography mass spectrometry (LC-MS/MS), and their binding to ACE was studied by molecular docking. The optimal processing conditions were 1:1 alkaline protease: compound protease, pH was 8.43, enzymolysis temperature was 44.32 °C, and enzymolysis time was 3.52 h. Under these conditions, the ACE inhibition rate reached 65.12%, and the inhibition rate after separation and purification was 80.68% (IC₅₀ = 0.9 mg/mL). Three novel peptides with ACE inhibitory activity were detected by LC-MS/MS, with sequences LVYP (Leu-Val-Tyr-Pro), VYPW(Val-Tyr-Pro-Trp) and YPWT(Tyr-Pro-Trp-Thr). Molecular docking revealed that the three novel peptides all established hydrogen bonds with the S1(Tyr523, Glu384, Ala354) and S2 (His353) pockets of ACE. Among them, LVYP, VYPW and YPWT, respectively, formed eleven hydrogen bonds, six hydrogen bonds and nine hydrogen bonds with ACE. The study revealed that these peptides have the potential for the development of novel ACE inhibitor drugs and provide a new avenue for high-value utilisation of mushrooms scraps.

Dual inhibition of the renin and angiotensin converting enzyme activities of aqueous extracts of 22 edible flower petals

In order to explore novel blood pressure-regulating substances and fulfill the high-value utilization of various edible flowers, the inhibitory activities of aqueous solutions of 22 edible flower petals extracts on renin and angiotensin converting enzyme (ACE) were investigated. The results showed that almost all the aqueous sample extracts demonstrated an inhibition of renin and/or ACE. The Rosa rugosa Thunb. (IC50 = 25.13 and 60.00 μg mL-1) and Paeonia suffruticosa Andr. (IC50 = 50.54 and 292.47 μg mL-1) extracts showed prominent dual inhibitory activity against renin and ACE. The antioxidant activities and content of total phenols and flavonoids of the aqueous sample extracts were tested, because the oxidative damage of blood vessels is closely related to the occurrence and development of hypertension. The correlation between the contents of total phenolic substances and flavonoids, and the functional activities was analyzed. Renin and ACE inhibitory activities, DPPH and ABTS free radical scavenging capacity, and iron reduction ability of different sample extracts were significantly positively correlated with the total phenolic content (p <0.01), whereby the correlation coefficients were 0.87, 0.83, 0.93, 0.95, and 0.93 respectively. It was indicated that the aqueous phenolic compounds in Rosa rugosa Thunb and Paeonia suffruticosa Andr extracts tended to show stronger renin and ACE inhibitory activities, and exhibited a potential prospect for auxiliary blood pressure control.

Novel Angiotensin-Converting Enzyme Inhibitory Peptides Identified from Walnut Glutelin-1 Hydrolysates: Molecular Interaction, Stability, and Antihypertensive Effects

In recent years, angiotensin-converting enzyme (ACE) inhibitory peptide has become a research hotspot because of its essential role in maintaining human blood pressure balance. In this study, two novel ACE inhibitory peptides of Val-Glu-Arg-Gly-Arg-Arg-lle-Thr-Ser-Val (Valine-Glutamate-Arginine-Glycine-Arginine-Arginine-Isoleucine-Threonine-Serine-Valine, VERGRRITSV) and Phe-Val-Ile-Glu-Pro-Asn-Ile-Thr-Pro-Ala (Phenylalanine-Valine-Isoleucine-Glutamate-Proline-Asparagine-Isoleucine-Threonine-Proline-Alanine, FVIEPNITPA) were isolated and purified from defatted walnut meal hydrolysates through a series of preparation processes including ultrafiltration, Sephadex G-15 gel chromatography, and reverse high performance liquid chromatography (RP-HPLC). Both peptides showed high ACE inhibitory activities. The molecular docking study revealed that VERGRRITSV and FVIEPNITPA were primarily attributed to the formation of strong hydrogen bonds with the active pockets of ACE. The binding free energies of VERGRRITSV and FVIEPNITPA with ACE were -14.99 and -14.69 kcal/mol, respectively. Moreover, these ACE inhibitory peptides showed good stability against gastrointestinal enzymes digestion and common food processing conditions (e.g., temperature and pH, sugar, and salt treatments). Furthermore, animal experiment results indicated that the administration of VERGRRITSV or FVIEPNITPA exhibited antihypertensive effects in spontaneously hypertensive rats. Our results demonstrated that walnut could be a potential source of bioactive peptides with ACE inhibitory activity.

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.

Advancement and prospects of production, transport, functional activity and structure-activity relationship of food-derived angiotensin converting enzyme (ACE) inhibitory peptides

Food-derived antihypertensive peptides have attracted increasing attention in functional foods for health promotion, due to their high biological activity, low toxicity and easy metabolism in the human body. Angiotensin converting enzyme (ACE) is a key enzyme that causes the increase in blood pressure in mammals. However, few reviews have summarized the current understanding of ACE inhibitory peptides and their knowledge gaps. This paper focuses on the food origins and production methods of ACE inhibitory peptides. Compared with conventional methods, the advanced technologies and emerging bioinformatics approaches have recently been applied for efficient and targeted release of ACE inhibitory peptides from food proteins. Furthermore, the transport and underlying mechanisms of ACE inhibitory peptides are emphatically described. Molecular modeling and the Michaelis-Menten equation can provide information on how ACE inhibitors function. Finally, we discuss the structure-activity relationships and other bio-functional properties of ACE inhibitory peptides. Molecular weight, hydrophobic amino acid residues, charge, amino acid composition and sequence (especially at the C-terminal and N-terminal) have a significant influence on ACE inhibitory activity. Some studies are required to increase productivity, improve bioavailability of peptides, evaluate their bio-accessibility and efficiency on reducing blood pressure to provide a reference for the development and application of health products and auxiliary treatment drugs.

Antimicrobial Peptides: A New Hope in Biomedical and Pharmaceutical Fields

Antibiotics are essential drugs used to treat pathogenic bacteria, but their prolonged use contributes to the development and spread of drug-resistant microorganisms. Antibiotic resistance is a serious challenge and has led to the need for new alternative molecules less prone to bacterial resistance. Antimicrobial peptides (AMPs) have aroused great interest as potential next-generation antibiotics, since they are bioactive small proteins, naturally produced by all living organisms, and representing the first line of defense against fungi, viruses and bacteria. AMPs are commonly classified according to their sources, which are represented by microorganisms, plants and animals, as well as to their secondary structure, their biosynthesis and their mechanism of action. They find application in different fields such as agriculture, food industry and medicine, on which we focused our attention in this review. Particularly, we examined AMP potential applicability in wound healing, skin infections and metabolic syndrome, considering their ability to act as potential Angiotensin-Converting Enzyme I and pancreatic lipase inhibitory peptides as well as antioxidant peptides. Moreover, we argued about the pharmacokinetic and pharmacodynamic approaches to develop new antibiotics, the drug development strategies and the formulation approaches which need to be taken into account in developing clinically suitable AMP applications.

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.

Identification of bioactive peptides released from in vitro gastrointestinal digestion of yam proteins (Dioscorea cayennensis)

Bioactive peptides have been broadly studied for their contribution to human health. This study aimed to identify bioactive peptides generated by in vitro gastrointestinal digestion of yam proteins. Yam protein concentrate (YPC) was submitted to simulated digestion. Gastric phase hydrolysate (GPH) and total gastrointestinal phase hydrolysate (GIPH) had their peptides identified by nanoLC-ESI-MS/MS. Peptide sequences were subjected to a database-driven (BIOPEP) bioactivity search. In vitro tests included: Antioxidant activity, DNA damage protection, ACE-inhibitory activity and antibacterial activity against the bacteria Escherichia coli, Salmonella sp. and Lysteria monocytogenes. Simulated digestion generated small peptides (mostly MW < 3500 Da), several of them with potential bioactive sequences predicted in silico. In both GPH and GIPH biological activities were detected, although GIPH displayed stronger DNA damage protection and antibacterial activity against Escherichia coli. The digestion of yam proteins releases promising biologically active peptides which can contribute to the prevention of bacterial infection and chronic degenerative diseases, with beneficial effects to human health.

Bioactive peptides in the management of lifestyle-related diseases: Current trends and future perspectives

Lifestyle-related diseases constitute a major concern in the twenty-first century, with millions dying worldwide each year due to chosen lifestyles and associated complications such as obesity, type 2 diabetes, hypertension, and hypercholesterolemia. Although synthetic drugs have been shown to be quite effective in the treatment of these conditions, safety of these compounds remains a concern. Natural alternatives to drugs include food-derived peptides are now being explored for the prevention and treatment of lifestyle-related complications. Peptides are fragments nascent in the primary protein sequences and could impart health benefits beyond basic nutritional advantages. Evidence suggests that by controlling adipocyte differentiation and lipase activities, bioactive peptides may be able to prevent obesity. Bioactive peptides act as agents against type 2 diabetes because of their ability to inhibit enzymatic activities of DPP-IV, α-amylase, and α-glucosidase. Moreover, bioactive peptides can act as competitive inhibitors of angiotensin-converting enzyme, thus eliciting an antihypertensive effect. Bioactive peptides may have a hypocholesterolemic effect by inhibiting cholesterol metabolism pathways and cholesterol synthesis. This review addresses current knowledge of the impact of food-derived bioactive peptides on lifestyle diseases. In addition, future insights on the clinical trials, allergenicity, cytotoxicity, gastrointestinal stability, and regulatory approvals have also been considered.

Prospects of cereal protein-derived bioactive peptides: Sources, bioactivities diversity, and production

Cereals account for a large proportion of the human diet and are an important source of protein. The preparation of cereal protein peptides is a good way to utilize these proteins. Cereal protein peptides have good application potential as antioxidant, antibacterial, anti-inflammatory and anticancer compounds, in lowering blood pressure, controlling blood sugar, and inhibiting thrombosis. This article reviews the literature on the functional properties, mechanisms of action, and applications of cereal protein peptides in the food industry with two perspectives, and summarizes the methods for their preparation and identification. The biologically active peptides derived from different grain proteins have varied main functional properties, which may be related to the differences in the amino acid composition and protein types of different grains. On this basis, the structure-activity relationship of cereal protein peptides was discussed. The advancement of identification technology makes the integration of bioinformatics and bioactive peptide research closer. Bioinformatics by combination of online database, computer simulation and experimental verification is helpful to in-deep study the structure-activity relationship of biologically active peptides, and improve efficiency in the process of obtaining target peptides with less cost. In addition, the application of cereal protein peptides in the food industry is also discussed.

Recently isolated food-derived antihypertensive hydrolysates and peptides: A review

Hypertension is a non-communicable disease characterized by elevated blood pressure, and a prominent metabolic syndrome of modern age. Food-borne bioactive peptides have shown considerable potencies as suitable therapeutic agents for hypertension. The peptide inhibition of the angiotensin I-converting enzyme (ACE) from its default biochemical conversion of Ang I to Ang II has been studied and more relatively adopted in several studies. This review offers an examination of the isolation of concomitant proteins in foods, their hydrolysis into peptides and the biofunctionality checks of those peptides based on their anti-hypertensive potentialities. Furthermore, critical but concise details about methodologies and analytical techniques used in the purification of such peptides are discussed. This review is a beneficial literature supplement for scholars and provides functional awareness material for the food-aligned alternative therapy for hypertension. In addition, it points researchers in the direction of adopting food materials and associated by-products as natural sources for the isolation biologically active peptides.

A Proline-Based Tectons and Supramolecular Synthons for Drug Design 2.0: A Case Study of ACEI

Proline is a unique, endogenous amino acid, prevalent in proteins and essential for living organisms. It is appreciated as a tecton for the rational design of new bio-active substances. Herein, we present a short overview of the subject. We analyzed 2366 proline-derived structures deposited in the Cambridge Structure Database, with emphasis on the angiotensin-converting enzyme inhibitors. The latter are the first-line antihypertensive and cardiological drugs. Their side effects prompt a search for improved pharmaceuticals. Characterization of tectons (molecular building blocks) and the resulting supramolecular synthons (patterns of intermolecular interactions) involving proline derivatives, as presented in this study, may be useful for in silico molecular docking and macromolecular modeling studies. The DFT, Hirshfeld surface and energy framework methods gave considerable insight into the nature of close inter-contacts and supramolecular topology. Substituents of proline entity are important for the formation and cooperation of synthons. Tectonic subunits contain proline moieties characterized by diverse ionization states: -N and -COOH(-COO-), -N+ and -COOH(-COO-), -NH and -COOH(-COO-), -NH+ and -COOH(-COO-), and -NH2+ and -COOH(-COO-). Furthermore, pharmacological profiles of ACE inhibitors and their impurities were determined via an in silico approach. The above data were used to develop comprehensive classification, which may be useful in further drug design studies.

Current Trends of Bioactive Peptides-New Sources and Therapeutic Effect

Generally, bioactive peptides are natural compounds of food or part of protein that are inactive in the precursor molecule. However, they may be active after hydrolysis and can be transported to the active site. Biologically active peptides can also be synthesized chemically and characterized. Peptides have many properties, including antihypertensive, antioxidant, antimicrobial, anticoagulant, and chelating effects. They are also responsible for the taste of food or for the inhibition of enzymes involved in the development of diseases. The scientific literature has described many peptides with bioactive properties obtained from different sources. Information about the structure, origin, and properties of peptides can also be found in many databases. This review will describe peptides inhibiting the development of current diseases, peptides with antimicrobial properties, and new alternative sources of peptides based on the current knowledge and documentation of their bioactivity. All these issues are part of modern research on peptides and their use in current health or technological problems in food production.