Identification of angiotensin converting enzyme and dipeptidyl peptidase-IV inhibitory peptides derived from oilseed proteins using two integrated bioinformatic approaches

Preparation, identification, and molecular docking of novel angiotensin-converting enzyme inhibitory peptides derived from rice-based distillers' spent cakes

BACKGROUND

Rice-based distillers' spent cake (RDSC), a by-product of the Chinese liquor (Baijiu) industry, is a potential source of angiotensin-converting enzyme (ACE) inhibitory peptide. Since ACE plays a crucial role in controlling hypertension, inhibition of ACE has been widely emphasized. The ACE inhibitory active peptide derived from by-products of food has been recognized as a safer and cheaper inhibitor.

RESULTS

Aimed to discover ACE-inhibiting active peptides in RDSC. Hydrolysis of RDSC by alcalase for 4 h followed by ultrafiltration yielded low-molecular-weight (< 3 kDa) fractions. Subsequently, a comprehensive method using a combination of liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) and LC-Q-Exactive-MS to identify the novel short peptides (3-5 amino acids residues; n = 7) and medium-sized peptides (more than 6 amino acids residues; n = 6). In vitro activity assay showed that the peptides KPFFPGL, GFPRPLL, GPPGVF, and VGK exhibited the highest activity with inhibitory concentration of 50% (IC50) of 11.63, 12.34, 19.55, and 33.54 μmol L-1. Molecular docking reveal that the active and inactive sites (Glu123, Asp121, Arg522, and Lys118) play important roles in enhancing the ACE inhibitory activity of peptides.

CONCLUSION

Here we report a comprehensive method that effectively extracted and identified the bioactive peptides from RDSC. Four highly active novel peptides may be the most promising candidates for functional foods against hypertension, provide significant information for enhancing value of rice-based distilled by-products. © 2024 Society of Chemical Industry.

Encapsulation of short-chain bioactive peptides (BAPs) for gastrointestinal delivery: a review

The majority of known peptides with high bioactivity (BAPs) such as antihypertensive, antidiabetic, antioxidant, hypocholesterolemic, anti-inflammatory and antimicrobial actions, are short-chain sequences of less than ten amino acids. These short-chain BAPs of varying natural and synthetic origin must be bioaccessible to be capable of being adsorbed systemically upon oral administration to show their full range of bioactivity. However, in general, in vitro and in vivo studies have shown that gastrointestinal digestion reduces BAPs bioactivity unless they are protected from degradation by encapsulation. This review gives a critical analysis of short-chain BAP encapsulation and performance with regard to the oral delivery route. In particular, it focuses on short-chain BAPs with antihypertensive and antidiabetic activity and encapsulation methods via nanoparticles and microparticles. Also addressed are the different wall materials used to form these particles and their associated payloads and release kinetics, along with the current challenges and a perspective of the future applications of these systems.

Identification, rapid screening, docking mechanism and in vitro digestion stability of novel DPP-4 inhibitory peptides from wheat gluten with ginger protease

To better understand the hypoglycemic potential of wheat gluten (WG), we screened dipeptidyl peptidase IV (DPP-4) inhibitory active peptides from WG hydrolysates. WG hydrolysates prepared by ginger protease were found to have the highest DPP-4 inhibitory activity among the five enzymatic hydrolysates, from which a 1-3 kDa fraction was isolated by ultrafiltration. Further characterization of the fraction with nano-HPLC-MS/MS revealed 1133 peptides. Among them, peptides with P'2 (the second position of the N-terminal) and P2 (the second position of the C-terminal) as proline residues (Pro) accounted for 12.44% and 43.69%, respectively. The peptides including Pro-Pro-Phe-Ser (PPFS), Ala-Pro-Phe-Gly-Leu (APFGL), and Pro-Pro-Phe-Trp (PPFW) exhibited the most potent DPP-4 inhibitory activity with IC50 values of 56.63, 79.45, and 199.82 μM, respectively. The high inhibitory activity of PPFS, APFGL, and PPFW could be mainly attributed to their interaction with the S2 pocket (Glu205 and Glu206) and the catalytic triad (Ser630 and His740) of DPP-4, which adopted competitive, mixed, and mixed inhibitory modes, respectively. After comparative analysis of PPFS, PPFW, and PPF, Ser was found to be more conducive to enhancing the DPP-4 inhibitory activity. Interestingly, peptides with P2 as Pro also exhibited good DPP-4 inhibitory activity. Meanwhile, DPP-4 inhibitory peptides from WG showed excellent stability, suggesting a potential application in type 2 diabetes (T2DM) therapy or in the food industry as functional components.

Effects of fermentation with Lactiplantibacillus plantarum NCU116 on the antihypertensive activity and protein structure of black sesame seed

Effects of fermentation by Lactobacillus Plantarum NCU116 on the antihypertensive potential of black sesame seed (BSS) and structure characteristics of fermented black sesame seed protein (FBSSP) were investigated. Angiotensin-I-converting enzyme (ACE) inhibition and zinc chelating ability of fermented black sesame seed hydrolysate (FBSSH) reached the highest of 60.78 ± 3.67 % and 2.93 ± 0.04 mg/mL at 48 h and 60 h of fermentation, respectively. Additionally, the antioxidant activities of FBSSH and surface hydrophobicity of FBSSP were increased noticeably by fermentation. The α-helix and β-rotation of FBSSP tended to decrease and increase, respectively, during fermentation. Correlation analysis indicated strong positive relationships between β-turn and ACE inhibition activity as well as zinc chelating ability with correlation coefficients r of 0.8976 and 0.8932. Importantly, novel ACE inhibitory peptides LLLPYY (IC50 = 12.20 μM) and ALIPSF (IC50 = 558.99 μM) were screened from FBSSH at 48 h using in silico method. Both peptides showed high antioxidant activities in vitro. Molecular docking analysis demonstrated that the hydrogen bond connected with zinc ions of ACE mainly attributed to the potent ACE inhibitory activity of LLLPYY. The findings indicated that fermentation by Lactobacillus Plantarum NCU116 is an effective method to enhance the antihypertensive potential of BSS.

Screening and Constructing of Novel Angiotensin I-Converting Enzyme Inhibiting Peptides from Walnut Protein Isolate and Their Mechanisms of Action: A Merged In Silico and In Vitro Study

Angiotensin I-converting enzyme (ACE)-inhibiting peptides were isolated from walnut protein isolate (WPI) using ultrasound-assisted extraction. This study aimed to assess the impact of ultrasonic pretreatment on the physicochemical properties of WPI. The optimal extraction conditions for WPI were determined as a 15-min ultrasonic treatment at 400 W. Subsequently, the hydrolysate exhibiting the highest in vitro ACE-inhibiting activity underwent further processing and separation steps, including ultrafiltration, ion exchange chromatography, liquid chromatography-tandem mass spectrometry, ADMET screening, and molecular docking. As a result of this comprehensive process, two previously unidentified ACE-inhibiting peptides, namely Tyr-Ile-Gln (YIQ) and Ile-Tyr-Gln (IYQ), were identified. In addition, a novel peptide, Ile-Lys-Gln (IKQ), was synthesized, demonstrating superior ACE-inhibiting activity and temperature stability. In silico analysis estimated an in vivo utilization rate of 21.7% for IKQ. These peptides were observed to inhibit ACE through an anti-competitive mechanism, with molecular docking simulations suggesting an interaction mechanism involving hydrogen bonding. Notably, both IYQ and IKQ peptides exhibited no discernible toxicity to HUVECs cells and promoted nitric oxide (NO) generation. These findings underscore the potential of ultrasonicated WPI in the separation of ACE-inhibiting peptides and their utility in the development of novel ACE inhibitors for functional food applications.

Antihypertensive peptide resources map of ribulose-1,5-bisphosphate carboxylase/oxygenases (RuBisCO) in angiosperms: Revealed by an integrated in silico and in vitro approach

As the most abundant protein on earth, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) has been considered a promising resource of functional foods. This study aimed to explore the full potential of plant RuBisCO proteins as precursors of antihypertensive peptides on a large scale. In total, 12,766 RuBisCO large subunit and 1,020 RuBisCO small subunit sequences of angiosperms were collected for simulated proteolysis and evaluation of antihypertensive potential, revealing a vast reservoir of antihypertensive peptides. Moreover, RuBisCO-derived novel antihypertensive peptides TTVW, TMW, and VPCL were identified with in vitro IC50 of 12.89 ± 0.82, 23.97 ± 1.02, and 339.12 ± 21.64 μM, respectively. Notably, TTVW and TMW are noncompetitive inhibitors predicted to bound adjacent to the catalytic region of ACE, while VPCL is a competitive inhibitor predicted to bound to the central active site inside ACE. Overall, this work provides a powerful theoretical guidance in developing antihypertensive functional foods utilizing plant RuBisCO.

Angiotensin I-Converting Enzyme Inhibitory Activity of Two Peptides Derived from In Vitro Digestion Products of Pork Sausage with Partial Substitution of NaCl by KCl

This study aimed to identify angiotensin I-converting enzyme (ACE) from in vitro digestion products of pork sausage with partial substitution of NaCl by KCl (PSRK). Peptides from in vitro digestion products of PSRK were identified through liquid chromatography with tandem mass spectrometry analysis coupled with de novo sequencing. Subsequently, the ACE inhibitory peptides LIVGFPAYGH and IVGFPAYGH were screened based on PeptideRanker, in silico absorption, molecular docking, and the determination of ACE inhibitory activity. In addition, the ACE inhibitory peptides LIVGFPAYGH and IVGFPAYGH were mixed-type inhibitors; these peptides' ACE inhibitory activities were expressed as the 50% inhibitory concentration (IC₅₀) values in vitro, which were 196.16 and 150.88 μM, respectively. After 2 h of incubation, LIVGFPAYGH and IVGFPAYGH could be transported through Caco-2 cell monolayers with paracellular passive diffusion. Furthermore, LIVGFPAYGH and IVGFPAYGH significantly increased the levels of ACE2 and nitric oxide while decreasing the levels of ACE, angiotensin II, and endothelin-1 in Ang I-treated human umbilical vein endothelial cells, indicating the ACE inhibitory effect of LIVGFPAYGH and IVGFPAYGH. In summary, LIVGFPAYGH and IVGFPAYGH from PSRK can be used as functional foods with antihypertensive activity.

Evaluation of oilseed proteins as precursors of antimicrobial peptides using bioinformatics method

In this study, the potential of oilseed proteins from soybean, peanut, sesame, sunflower seed and flaxseed as antimicrobial peptide (AMP) precursors was assessed using the bioinformatics method. Thirty-four novel potential AMPs were obtained by in silico hydrolysis of 12 oilseed protein sequences, and 11 of them were positive in all four algorithm tests in CAMP_R3. Among the six proteases analyzed, trypsin cleaved soybean, peanut, sesame and sunflower seed proteins most effectively to generate AMPs, with three, four, two and two AMPs obtained, respectively. Subtilisin was most effective for flaxseed AMPs release, obtaining three AMPs. More than 85% of AMPs were predicted to be cationic peptides, and some AMPs were hydrophobic. These potential AMPs were classified as non-toxic peptides, and 15 peptides were non-allergenic. All the AMPs were unstable to digestive enzymes according to in silico simulated digestion. The results of this study provide a theoretical basis for further development of AMPs using oilseed proteins.

In silico identification of novel ACE and DPP-IV inhibitory peptides derived from buffalo milk proteins and evaluation of their inhibitory mechanisms

The capacity of buffalo milk proteins to release bioactive peptides was evaluated and novel bioactive peptides were identified. The sequential similarity between buffalo milk proteins and their cow counterparts was analysed. Buffalo milk proteins were simulated to yield theoretical peptides via in silico proteolysis. The potential of selected proteins to release specific bioactive peptides was evaluated by the A value obtained from the BIOPEP-UWM database (Minkiewicz et al. in Int J Mol Sci 20(23):5978, 2019). Buffalo milk protein is a suitable precursor to produce bioactive peptides, particularly dipeptidyl peptidase IV (DPP-IV) and angiotensin I-converting enzyme (ACE) inhibitory peptides. Two novel ACE inhibitory peptides (KPW and RGP) and four potential DPP-IV inhibitory peptides (RGP, KPW, FPK and KFTW) derived from in silico proteolysis of buffalo milk proteins were screened using different integrated bioinformatic approaches (PeptideRanker, Innovagen, peptide-cutter and molecular docking). The Lineweaver-Burk plots showed that KPW (IC₅₀ = 136.28 ± 10.77 μM) and RGP (104.72 ± 8.37 μM) acted as a competitive inhibitor against ACE. Similarly, KFTW (IC₅₀ = 873.92 ± 32.89 μM) was also a competitive inhibitor of DPP-IV, while KPW and FPK (82.52 ± 10.37 and 126.57 ± 8.45 μM, respectively) were mixed-type inhibitors. It should be emphasized that this study does not involve any clinical trial.

Secrets behind Protein Sequences: Unveiling the Potential Reasons for Varying Allergenicity Caused by Caseins from Cows, Goats, Camels, and Mares Based on Bioinformatics Analyses

This study systematically investigated the differences in allergenicity of casein in cow milk (CM), goat milk (GM), camel milk (CAM), and mare milk (MM) from protein structures using bioinformatics. Primary structure sequence analysis reveals high sequence similarity between the α-casein of CM and GM, while all allergenic subtypes are likely to have good hydrophilicity and thermal stability. By analyzing linear B-cell epitope, T-cell epitope, and allergenic peptides, the strongest casein allergenicity is observed for CM, followed by GM, and the casein of MM has the weakest allergenicity. Meanwhile, 7, 9, and 16 similar or identical amino acid fragments in linear B-cell epitopes, T-cell epitopes, and allergenic peptides, respectively, were observed in different milks. Among these, the same T-cell epitope FLGAEVQNQ was shared by κ-CN in all four different species' milk. Epitope results may provide targets of allergenic fragments for reducing milk allergenicity through physical or/and chemical methods. This study explained the underlying secrets for the high allergenicity of CM to some extent from the perspective of casein and provided new insights for the dairy industry to reduce milk allergy. Furthermore, it provides a new idea and method for comparing the allergenicity of homologous proteins from different species.

Antimicrobial bioactive peptides from goat Milk proteins: In silico prediction and analysis

The main goal of this study was to assess the potential proteins of goat milk (i.e. α-s1-casein, α-s2-casein, β-casein, κ-casein, α-lactoglobulin and β-lactalbumin) as precursors of antimicrobial peptides (AMPs). Bioinformatics tools such as BIOPEP-UWM (enzyme action) were used for the in silico gastrointestinal digestion via a cocktail of pepsin, trypsin, and chymotrypsin A. The antimicrobial activity of peptides was predicted by using four algorithms, including Random Forest, Support Vector Machines, Artificial Neural Network and Discriminant Analysis on CAMPR3 online server, which works on Hidden Markov Models. Different online tools predicted the physiochemical properties, allergenicity, and toxicity of peptides as well. In silico gastrointestinal digestion simulation of proteins by enzymes cocktail yielded a total of 83 potential AMPs, with thirteen peptides being confident by all four algorithms. More AMPs were released from β-casein (21) than from β-lactoglobulin (16), α-s1-casein (15), α-s2-casein (12), κ-casein (11) and α-lactalbumin (9). A total of 17 peptides were cationic, and the majority of the peptides were extended AMPs. These peptides were released from α-s1-casein (SGK, IQK), α-s2-casein (SIR, AIH, TQPK), β-casein (GPVR, AVPQR, AIAR, GVPK, SQPK, PVPQK, IH, VPK), k-casein (AIPPK, QQR, IAK, TVPAK). All of the AMPs were anticipated to be non-toxic, and 54 of the 83 peptides were confirmed to be non-allergic, with the remaining 29 suspected of being allergenic and 31 to be predicted to have good water solubility. Further the molecular docking was used to evaluate the potent dihydropteroate synthase (DHPS) inhibitors. On the basis of ligand binding energy, 17 predicted AMPs were selected and then analyzed by AutoDock tools. Among the 17 AMPs, 3 AMPs were predicted as high-potent antimicrobial. Based on these findings, in silico investigations reveal that proteins of goat milk are a potential source of AMPs. These peptides can be synthesized and improved for use in the food sector. PRACTICAL APPLICATIONS: Goat milk is regarded as a high-quality milk protein source. According to this study, goat milk protein is a possible source of AMPs, and therefore, most important AMPs can be synthesized and developed for use in the food sector.

Identification of antidiabetic peptides derived from in silico hydrolysis of three ancient grains: Amaranth, Quinoa and Chia

The antidiabetic potential of bioactive peptides derived from simulated gastrointestinal digestion (SGID) of proteins present in amaranth quinoa and chia was evaluated using their bioactivity profile and theoretical interaction with DPP-IV and α-glucosidases. In silico SGID generated 52 different fragments with in vitro antidiabetic activity where fragments PW, PF, PPG, PM, SW, IW, SF, PP, PPL, PG, PY, VW and PL scored highly in bioactivity probability, with molecular weights ranging from 172.2 to 325.44 Da; positive bulkiness index and hydrophobicity (except PP and PY) and no toxic properties. Fragments IW and PW presented the lowest free energy values for enzymes DPP-IV, maltase-glucoamylase, pancreatic α-amylase and sucrase-isomaltase (-8.2, -7.5, -7.7 and -7.5 kcal/mol; and -7.8, -7.4, -8.2, -7.4 kcal/mol respectively) We can conclude that proteins from amaranth, quinoa and chia may be a good source of antidiabetic BP and may exert antidiabetic activity through the release of BP after digestion.

Conventional and in silico approaches to select promising food-derived bioactive peptides: A review

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Seaweed and edible insects are considered new sources of bioactive peptides.

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Conventional approaches are necessary to validate the bioactivity of peptides.

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Bioinformatics tools accelerate the obtaining of bioactive peptides.

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The integrated approach is a promising strategy to obtain bioactive peptides.

The interest for food-derived bioactive peptides, either from common or unconventional sources, has increased due to their potential therapeutic effect against a wide range of diseases. The study of such bioactive peptides using conventional methods is a long journey, expensive and time-consuming. Hence, bioinformatic approaches, which can not only help to predict the formation of bioactive peptides from any known protein source, but also to analyze the protein structure/function relationship, have gained a new meaning in this scientific field. Therefore, this review aims to provides an overview of conventional characterization methods and the most recent advances in the field of in silico approaches for predicting and screening promising food-derived bioactive peptides.

Exploration of bioactive peptides from various origin as promising nutraceutical treasures: In vitro, in silico and in vivo studies

The current health scenarios describe growing public health problems, such as diabetes, hypertension and cancer. Therefore, researchers focused on studying these health issues are interested in exploring bioactive compounds from different food sources. Among them, bioactive peptides have garnered huge scientific interest because of their multifunctional biological activities such as antioxidative, antimicrobial, antihypertensive, anticancer, antidiabetic, immunomodulatory effect. They can be used as food and pharmaceutical ingredients with a great potential against disease targets. This review covers methods of production in general for several peptides obtained from various food sources including seed, milk and meat, and described their biological activities. Particular focus was given to bioinformatic tools to advance quantification, detection and characterize each peptide sequence obtained from different protein sources with predicted biological activity. Besides, various in vivo studies have been discussed to provide a better understanding of their physiological functions, which altogether could provide valuable information for their commercialization in future foods.

Identification of in vitro angiotensin-converting enzyme and dipeptidyl peptidase IV inhibitory peptides from draft beer by virtual screening and molecular docking

BACKGROUND

Hypertension and diabetes are two kinds of senile diseases which often occur simultaneously. The commonly used drugs in clinic may produce certain side effects. Food-derived polypeptide is a kind of polypeptide with great development potential, which has many functions of regulating human physiological function. Beer is rich in nutrition but there are few researches on bioactive peptides in beer.

RESULTS

In this study, a rapid virtual screening method was established to obtain bioactive peptides from Tsingtao draft beer. The peptide sequence was analyzed by ultra-performance liquid chromatography-quadrupole-Orbitrap-tandem mass spectrometry (UPLC-Q-Orbitrap-MS² ), and 50 peptides were identified. Eight peptides with potential biological activities were screened by using Peptide Ranker software and previous literature references. On the basis of absorption prediction, toxicity prediction, and molecular docking analysis, LNFDPNR and LPQQQAQFK were finally confirmed. The molecular docking results showed that two peptides could bind angiotensin-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV) tightly by hydrogen bonding and hydrophobic interaction. The in vitro activity evaluation results showed that two peptides had obvious ACE and DPP-IV inhibitory activity.

CONCLUSION

This study established a method for rapidly screening bioactive peptides from Tsingtao draft beer, screened two ACE and DPP-IV inhibitory peptides in beer and analyzed their active action mechanism. This article may have great theoretical significance and practical value to further explore the health function of beer. © 2021 Society of Chemical Industry.

In silico proteolysis and analysis of bioactive peptides from sequences of fatty acid desaturase 3 (FAD3) of flaxseed protein

Flaxseed (Linum usitatissimum), commonly known as linseed is an oilseed crop, emerging as an important and functional ingredient of food and has been paid more attention due to its nutritional value as well as beneficial effects. It is mainly rich in is α-linolenic acid (ALA, omega-3 fatty acid), fibres and lignans that have potential health benefits in reducing cardiovascular diseases, diabetes, osteoporosis, atherosclerosis, cancer, arthritis, neurological and autoimmune disorders. Due to its richness in omega-3 fatty acid, a group of enzymes known as fatty acid desaturases (FADs) mainly introduce double bonds into fatty acids’ (FAs) hydrocarbon chains that produce unsaturated fatty acids. Fatty acid desaturase 3 (FAD3), the commonest microsomal enzyme of omega-3 fatty acid, synthesizes linolenic acid (C18:3) from linoleic acid located in endoplasmic reticulum (ER) facing towards the cytosol. The emerging field of bioinformatics and large number of databases of bioactive peptides, helps in providing time-saving and efficient method for identification of potential bioactivities of any protein. In this study, 10 unique sequences of FAD3 from flaxseed protein have been used for in silico proteolysis and releasing of various bioactive peptides using three plant proteases, namely ficin, papain and stem bromelain, that are evaluated with the help of BIOPEP database. Overall, 20 biological activities were identified from these proteins. The results showed that FAD3 protein is a potential source of peptides with angiotensin-I-converting enzyme (ACE) inhibitory and dipeptidyl peptidase-IV (DPP-IV) activities, and also various parameters such as ∑A, ∑B, A_E, W, B_E, V and DHt were also calculated. Furthermore, PeptideRanker have been used for screening of novel promising bioactive peptides. Various bioinformatics tools also used to study protein’s physicochemical properties, peptide’s score, toxicity, allergenicity aggregation, water solubility, and drug likeliness. The present work suggests that flaxseed protein can be a good source of bioactive peptides for the synthesis of good quality and quantity of oil, and in silico method helps in investigating and production of functional peptides.

Screening and mechanisms of novel angiotensin-I-converting enzyme inhibitory peptides from rabbit meat proteins: A combined in silico and in vitro study

Bioactive peptides derived from food proteins have various physiological roles and have attracted increasing attention in recent years. In this study, two novel ACE inhibitory peptides (EACF and CDF), screened from rabbit meat proteins using in silico methods, exhibited strong inhibitory effects in vitro. EACF and CDF were competitive and non-competitive inhibitors with half-maximal inhibitory concentrations of 41.06 ± 0.82 µM and 192.17 ± 2.46 µM, respectively. Molecular docking experiments revealed that EACF established eight H-bond interactions in the S1 and S2 pockets, and a metal-acceptor interaction with Zn 701. CDF shared four H-bond interactions in the S1 pocket of ACE. The results suggested that rabbit meat proteins could be a suitable material for the preparation of ACE inhibitory peptides, and that virtual screening is an effective, accurate and promising method for the discovery of novel active peptides.

Bioactive Peptides as Potential Nutraceuticals for Diabetes Therapy: A Comprehensive Review

Diabetes mellitus is a major public health concern associated with high mortality and reduced life expectancy. The alarming rise in the prevalence of diabetes is linked to several factors including sedentary lifestyle and unhealthy diet. Nutritional intervention and increased physical activity could significantly contribute to bringing this under control. Food-derived bioactive peptides and protein hydrolysates have been associated with a number health benefits. Several peptides with antidiabetic potential have been identified that could decrease blood glucose level, improve insulin uptake and inhibit key enzymes involved in the development and progression of diabetes. Dietary proteins, from a wide range of food, are rich sources of antidiabetic peptides. Thus, there are a number of benefits in studying peptides obtained from food sources to develop nutraceuticals. A deeper understanding of the underlying molecular mechanisms of these peptides will assist in the development of new peptide-based therapeutics. Despite this, a comprehensive analysis of the antidiabetic properties of bioactive peptides derived from various food sources is still lacking. Here, we review the recent literature on food-derived bioactive peptides possessing antidiabetic activity. The focus is on the effectiveness of these peptides as evidenced by in vitro and in vivo studies. Finally, we discuss future prospects of peptide-based drugs for the treatment of diabetes.

Interactions of C. frondosa-derived inhibitory peptides against angiotensin I-converting enzyme (ACE), α-amylase and lipase

The study illustrates the molecular mechanisms by which marine-derived peptides exhibited different structures and inhibition functions to concurrently inhibit multiple enzymes involved in chronic diseases. Peptides (2 mg/mL) exhibited inhibition against angiotensin-converting enzyme (ACE, inhibition of 52.2-78.8%), pancreatic α-amylase (16.3-27.2%) and lipase (5.3-17.0%). Further in silico analyses on physiochemistry, bioactivity, safety and interaction energy with target enzymes indicated that one peptide could inhibit multiple enzymes. Peptide FENLLEELK potent in inhibiting both ACE and α-amylase showed different mechanisms: it had ordered extended structure in ACE active pocket with conventional H-bond towards Arg₅₂₂ which is the ligand for activator Cl^-, while the peptide folded into compact "lariat" conformation within α-amylase active site and the K residue in peptide formed intensive H-bonds and electrostatic interactions with catalytic triad Asp₁₉₇ - Asp₃₀₀ - Glu₂₃₃. Another peptide APFPLR showed different poses in inhibiting ACE, α-amylase and lipase, and it formed direct interactions to lipase catalytic residues Phe₇₇ & His₂₆₃.

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.

Protease Inhibitors Purified from the Canola Meal Extracts of Two Genetically Diverse Genotypes Exhibit Antidiabetic and Antihypertension Properties

Valorization of vegetable oil waste residues is gaining importance due to their high protein and polyphenol contents. Protease inhibitors (PIs), proteins from these abundantly available waste residues, have recently gained importance in treating chronic diseases. This research aimed to use canola meal of genetically diverse Brassica napus genotypes, BLN-3347 and Rivette, to identify PIs with diverse functionalities in therapeutic and pharmacological applications. The canola meal PI purification steps involved: native PAGE and trypsin inhibition activity, followed by ammonium sulfate fractionation, anion exchange, gel filtration, and reverse-phase chromatography. The purified PI preparations were characterized using SDS-PAGE, isoelectric focusing (IEF), and N terminal sequencing. SDS-PAGE analysis of PI preparations under native reducing and nonreducing conditions revealed three polymorphic PIs in each genotype. The corresponding IEF of the genotype BLN-3347, exhibited three acidic isoforms with isoelectric points (pI) of 4.6, 4.0, and 3.9, while Rivette possessed three isoforms, exhibiting two basic forms of pI 8.65 and 9.9, and one acidic of pI 6.55. Purified PI preparations from both the genotypes displayed dipeptidyl peptidase-IV (DPP-IV) and angiotensin-converting enzyme (ACE) inhibition activities; the BLN-3347 PI preparation exhibited a strong inhibitory effect with lower IC₅₀ values (DPP-IV 37.42 µg/mL; ACE 129 µg/mL) than that from Rivette (DPP-IV 67.97 µg/mL; ACE 376.2 µg/mL). In addition to potential human therapy, these highly polymorphic PIs, which can inhibit damaging serine proteases secreted by canola plant pathogens, have the potential to be used by canola plant breeders to seek qualitative trait locus (QTLs) linked to genes conferring resistance to canola diseases.

Comparison of alcalase- and pepsin-treated oilseed protein hydrolysates - Experimental validation of predicted antioxidant, antihypertensive and antidiabetic properties

There is emerging evidence on the importance of food-derived bioactive peptides to promote human health. Compared with animal derived proteins, plant proteins, in particular oilseed proteins, are considered as affordable and sustainable sources of bioactive peptides. Based on our previous bioinformatic analysis, five oilseed proteins (flaxseed, rapeseed, sunflower, sesame and soybean) were enzymatically hydrolysed using alcalase and pepsin (pH 1.3 and pH 2.1). Further, low molecular weight (Mw ​< ​3 ​kDa) fractions were generated using ultrafiltration. The protein hydrolysates and their low Mw fractions were evaluated for their in vitro antioxidant, antihypertensive and antidiabetic capabilities, in comparison with samples obtained from two dairy proteins (whey and casein). Apart from dipeptidyl-peptidase IV inhibition, significantly stronger bioactivities were detected for the low Mw fractions. In partial agreement with in silico predictions, most oilseed hydrolysates exerted comparable angiotensin-converting enzyme inhibitory capability to dairy proteins, whilst whey protein was the most promising source of dipeptidyl-peptidase IV inhibitors. Apart from alcalase-treated soybean, dairy proteins were more efficient in releasing antioxidant peptides as compared to oilseed proteins. On the other hand, soybean protein hydrolysates showed the highest α-glucosidase inhibitory activity amongst all protein sources. Overall, there was limited correlation between in silico predictions and in vitro experimental results. Nevertheless, our results indicate that oilseed proteins have potential as bioactive peptide sources, and they might therefore be suitable replacers for dairy proteins as well as good sources for development of functional foods.

Prediction and analysis of antimicrobial peptides from rapeseed protein using in silico approach

The purpose of this study was to evaluate the potential of rapeseed proteins including Napin, Cruciferin, and Oleosin as precursors of antimicrobial peptides (AMPs), and to investigate physicochemical properties, secondary structures, toxicity, and allergenicity of AMPs using several bioinformatics tools such as BIOPEP, CAMP, APD, SOPMA, ToxinPred, and AllergenFP. A total of 26 novel AMPs were obtained by in silico hydrolysis using nine proteases, and six peptides were tested positive by all the four algorithms including Random Forest (RF), Support Vector Machines (SVM), Artificial Neural Network (ANN), and Discriminant Analysis (DA). More AMPs were generated from Cruciferin than from Napin and Oleosin. Trypsin was the most effective enzyme for AMPs production compared with other used proteases. About two-third of peptides were cationic. Interestingly, most peptides were extended AMPs. All AMPs were predicted to be non-toxic, and 14 peptides were non-allergenic. These results indicate that rapeseed protein is a good potential source of AMPs as demonstrated by in silico analyses and the theoretical knowledge obtained provides a basis for further development and production of rapeseed AMPs. PRACTICAL APPLICATIONS: Rapeseed protein is a high-quality plant protein resource. However, it is usually used as animal feed or fertilizer. Effective enzymatic hydrolysis of rapeseed protein can release bioactive peptides and improve the utilization value. This study indicates that rapeseed protein is a good potential source of AMPs as demonstrated by in silico analyses. The theoretical knowledge obtained provides a basis for further development and production of rapeseed AMPs.

SARS-CoV-2 spike protein-, main protease- and papain-like-protease-targeting peptides from seed proteins following gastrointestinal digestion: An in silico study

BACKGROUND

The anti-COVID-19 potential of phytochemicals was investigated in numerous studies, but efficacy of peptides released by seed proteins upon gastrointestinal (GI) digestion is underexplored.

PURPOSE

This study investigated whether multi-target anti-COVID-19 peptides could be released from edible seeds following GI digestion, by using in silico and molecular docking approaches.

METHODS

Nineteen seed storage proteins from Chenopodium quinoa (quinoa), Sesamum indicum (sesame), Brassica napus (rape), Helianthus annuus (sunflower) and Cucurbita maxima (pumpkin) seeds were subjected to in silico GI digestion, in order to detect the released peptides with high GI absorption that concurrently target the spike protein, main protease and papain-like protease of SARS-CoV-2.

RESULTS

Molecular docking study revealed that 36 peptides with high GI absorption, out of the 1593 peptides released from seed proteins, could bind to the binding or catalytic sites of the spike protein, main protease and papain-like protease of SARS-CoV-2, after GI digestion. Among the five seeds, quinoa was predicted to release the largest number (27) of multi-target peptides. When compared with PIY (Pro-Ile-Tyr), a high-GI-absorption fragment released from a potential anti-COVID-19 peptide, pumpkin-derived peptide PW (Pro-Trp) could bind more strongly to SARS-CoV-2 spike protein. PW was superior to some previously reported anti-SARS-CoV-2 phytochemicals when binding affinities towards the three viral targets were compared.

CONCLUSION

Edible seeds are a potential source of anti-COVID-19 peptides upon GI digestion, hence they should be considered as an alternative to assist in the treatment and management of COVID-19.

Techniques, perspectives, and challenges of bioactive peptide generation: A comprehensive systematic review

Due to the digestible refractory and absorbable structures of bioactive peptides (BPs), they could induce notable biological impacts on the living organism. In this regard, the current study was devoted to providing an overview regarding the available methods for BPs generation by the aid of a systematic review conducted on the published articles up to April 2019. In this context, the PubMed and Scopus databases were screened to retrieve the related publications. According to the results, although the characterization of BPs mainly has been performed using enzymatic and microbial in-vitro methods, they cannot be considered as suitable techniques for further stimulation of digestion in the gastrointestinal tract. Therefore, new approaches for both in-vivo and in-silico methods for BPs identification should be developed to overcome the obstacles that belonged to the current methods. The purpose of this review was to compile the recent analytical methods applied for studying various aspects of food-derived biopeptides, and emphasizing generation at in vitro, in vivo, and in silico.

Optimization of Sorghum Kafirin Extraction Conditions and Identification of Potential Bioactive Peptides

The interest in extracting kafirins (KAF), the main storage protein from sorghum grain has recently increased due to its gluten-free content and the significant scientific evidence showing the health benefits of the bioactive peptides from cereal grains in human diets. The objectives were to obtain the highest percentage of KAF extraction using amyloglucosidase as pretreatment to increase the extraction yield and predict the bioactive peptides in the KAF. In this study, pretreatments with amyloglucosidase increased the extraction yield of KAF compared with extraction methods using only ethanol and sodium metabisulfite. Two protein fragment sequences were identified from KAF extract and were evaluated for potential bioactive peptide using the BIOPEP-UWM database, which suggest that KAF proteins from white sorghum may be considered as good precursors of dipeptidyl peptidase-inhibitor, angiotensin-converting enzyme inhibitor, antioxidant and hypotensive peptides following chymotrypsin, thermolysin, and subtilisin and their combination. Average scores aligned using PeptideRanker confirmed KAF proteins' potential sources of bioactive peptides with over 5 peptides scored over 0.8. In addition, 31 unexplored peptide sequences that could have biological activity were identified. Our results suggest that KAF can be used in the peptide productions with potential biological activity and beyond.

Antidiabetic Food-Derived Peptides for Functional Feeding: Production, Functionality and In Vivo Evidences

Bioactive peptides released from the enzymatic hydrolysis of food proteins are currently a trending topic in the scientific community. Their potential as antidiabetic agents, by regulating the glycemic index, and thus to be employed in food formulation, is one of the most important functions of these peptides. In this review, we aimed to summarize the whole process that must be considered when talking about including these molecules as a bioactive ingredient. In this regard, at first, the production, purification and identification of bioactive peptides is summed up. The detailed metabolic pathways described included carbohydrate hydrolases (glucosidase and amylase) and dipeptidyl-peptidase IV inhibition, due to their importance in the food-derived peptides research field. Then, their characterization, concerning bioavailability in vitro and in situ, stability and functionality in food matrices, and ultimately, the in vivo evidence (from invertebrate animals to humans), was described. The future applicability that these molecules have due to their biological potential as functional ingredients makes them an important field of research, which could help the world population avoid suffering from several diseases, such as diabetes.

Novel dipeptidyl peptidase-IV and angiotensin-I-converting enzyme inhibitory peptides released from quinoa protein by in silico proteolysis

Quinoa protein has been paid more and more attention because of its nutritional properties and beneficial effects. With the development of bioinformatics, bioactive peptide database and computer-assisted simulation provide an efficient and time-saving method for the theoretical estimation of potential bioactivities of protein. Therefore, the potential of quinoa protein sequences for releasing bioactive peptides was evaluated using the BIOPEP database, which revealed that quinoa protein, especially globulin, is a potential source of peptides with dipeptidyl peptidase-IV (DPP-IV) and angiotensin-I-converting enzyme (ACE) inhibitory activities. Three plant proteases, namely papain, ficin, and stem bromelain, were employed for the in silico proteolysis of quinoa protein. Furthermore, four tripeptides (MAF, NMF, HPF, and MCG) were screened as novel promising bioactive peptides by PeptideRanker. The bioactivities of selected peptides were confirmed using chemical synthesis and in vitro assay. The present work suggests that quinoa protein can serve as a good source of bioactive peptides, and in silico approach can provide theoretical assistance for investigation and production of functional peptides.

A biotechnological approach for the production of branched chain amino acid containing bioactive peptides to improve human health: A review

Improper nutrition provokes many types of chronic diseases and health problems, which consequently are associated with particularly high costs of treatments. Nowadays, consumer's interest in healthy eating is shifting towards specific foods or food ingredients. As a consequence, bioactive peptides as a promising source of health promoting food additives are currently an intensely debated topic in research. Process design is still on its early stages and is significantly influenced by important preliminary decisions. Thus, parameters like peptide bioactivity within the product, selection of the protein source, enzyme selection for hydrolysis, peptide enrichment method, as well as stability of the peptides within the food matrix and bioavailability are sensitive decision points, which have to be purposefully coordinated, as they are directly linked to amino acid content and structure properties of the peptides. Branched chain amino acids (BCAA) are essential components for humans, possessing various important physiologic functions within the body. Incorporated within peptide sequences, they may induce dual functions, when used as nutraceuticals in functional food, thus preserving the foodstuff and prevent several widespread diseases. Furthermore, there is evidence that consuming this peptide-class can be a nutritional support for elderly people or improve human health to prevent diseases caused by incorrect nutrition. Based on the knowledge about the role of BCAA within various peptide functions, discussed in the review, special attention is given to different approaches for systematic selection of the protein source and enzymes used in hydrolysis, as well as suitable peptide enrichment methods, thereby showing current trends in research.