Identification of novel dipeptidyl peptidase-IV and angiotensin-I-converting enzyme inhibitory peptides from meat proteins using in silico analysis

A comparative study on antidiabetic and anti-inflammatory activities of fermented whey and soy protein isolates and the release of biofunctional peptides: an in vitro and in silico studies

BACKGROUND

This study aims to evaluate the antidiabetic and anti-inflammatory activities of Lacticaseibacillus rhamnosus (M9) MTCC 25516 during the fermentation of whey and soy protein isolates. It also seeks to characterize protein profiles, identify multifunctional peptides, and assess structural changes using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional (2D) gel electrophoresis, Fourier-transform infrared (FTIR) spectroscopy, and confocal laser scanning microscopy (CLSM).

RESULTS

Fermentation with Lacticaseibacillus rhamnosus (M9) significantly enhanced antidiabetic activity, with optimal peptide production at a 25 mL L-1 inoculation rate for 48 h at 37 °C. Proteolytic activity reduced inflammatory markers (IL-6, TNF-α, IL-1β, NO) in RAW 267.4 cells. SDS-PAGE and 2D gel electrophoresis revealed distinct protein profiles, with 19 and 49 protein spots in whey and soy isolates, respectively. Reverse-phase high-performance liquid chromatography (RP-HPLC) identified multifunctional peptides, and FTIR spectroscopy confirmed structural changes post-fermentation. Confocal microscopy further revealed protein modifications.

CONCLUSION

Fermentation of whey and soy protein isolates with Lacticaseibacillus rhamnosus (M9) enhances antidiabetic and anti-inflammatory properties. Optimal conditions (25 mL L-1 inoculation, 48-h incubation) improved peptide production, with analytical techniques confirming structural and functional changes. These findings suggest fermented protein isolates could be valuable in functional foods with health benefits. © 2025 Society of Chemical Industry.

Angiotensin-Converting Enzyme (ACE)-Inhibitor Activity of Novel Peptides Derived from Porcine Liver and Placenta

Peptides isolated from various biological materials are potential sources for novel angiotensin-converting enzyme (ACE) inhibitors. Here, the ACE-inhibitory activity of peptides derived from papain-digested hydrolysates of porcine liver and placenta were investigated. A high-throughput method was developed to identify potential bioactive peptides from the hydrolysates using in silico enzymatic cleavage, HPLC-MS/MS, and bioinformatics tools. Four peptides (FWG, MFLG, SDPPLVFVG, and FFNDA) were selected based on their predicted bioactivity, then synthesised and tested for ACE inhibition. All samples demonstrated ACE-inhibitory activity, with FWG and MFLG showing greater potency than SDPPLVFVG and FFNDA. The placenta hydrolysate outperformed both the liver hydrolysate and synthetic peptides in ACE inhibition, possibly due to it containing a higher proportion of dipeptides. The synthetic peptides' IC50 values were comparable to those reported for porcine muscle-derived peptides in previous studies. While less potent than the commercial ACE inhibitor captopril, the identified peptides showed promising ACE-inhibitory activity. This research demonstrates the potential of porcine liver and placenta as sources of novel ACE-inhibitory peptides and highlights the effectiveness of the developed high-throughput method for identifying bioactive peptides; this method could subsequently be adapted to other peptide sources, facilitating the development of innovative functional foods or nutraceuticals.

Functional and Bioactive Benefits of Selected Microalgal Hydrolysates Assessed In Silico and In Vitro

BIOPEP-UWM, a peptide database, contains 5128 peptides from a myriad of resources. Five listed peptides are Angiotensin-I-converting enzyme (ACE-1; EC3.4.15.1) inhibitory peptides derived from a red alga, while two from Chlorella vulgaris have anti-cancer and antioxidative bioactivities. Herein, we describe a process combining hydrolysis with two enzymes, Alcalase and Viscozyme, and filtration to generate protein-rich, bioactive peptide-containing hydrolysates from mixed species of Chlorella sp. and Scenedesmus sp. The potential of generated algal hydrolysates to act as food ingredients was determined by assessment of their techno-functional (foaming, emulsification, solubility, water holding, and oil holding capacity) properties. Bioactive screening of hydrolysates in vitro combined with mass spectrometry (MS) and in silico predictions identified bioactive and functional hydrolysates and six novel peptides. Peptides derived from Chlorella mix have the sequences YDYIGNNPAKGGLF and YIGNNPAKGGLF with predicted anti-inflammatory (medium confidence) and umami potential. Peptides from Scenedesmus mix have sequences IEWYGPDRPKFL, RSPTGEIIFGGETM, TVQIPGGERVPFLF, and IEWYGPDRPKFLGPF with predicted anti-inflammatory, anti-diabetic, and umami attributes. Such microalgal hydrolysates could provide essential amino acids to consumers as well as tertiary health benefits to improve human global health.

In Silico Hydrolysis of Lupin (Lupinus angustifolius L.) Conglutins with Plant Proteases Releases Antihypertensive and Antidiabetic Peptides That Are Bioavailable, Non-Toxic, and Gastrointestinal Digestion Stable

Lupin (Lupinus angustifolius L.) proteins are potential sources of bioactive peptides (LBPs) that can inhibit dipeptidyl peptidase IV (DPP-IV) and angiotensin I-converting enzyme (ACE-I) activity. However, the capacity of different enzymes to release LBPs, the pharmacokinetic and bioactivities of the peptides released, and their binding affinities with the active sites of DPP-IV and ECA-I are topics scarcely addressed. Therefore, we used in silico hydrolysis (BIOPEP-UWM platform) with various enzymes to predict the release of LBPs. Among the bioactive peptides identified in lupin proteins (n = 4813), 2062 and 1558 had DPP-IV and ACE-I inhibitory activity, respectively. Ficin, bromelain, and papain released the highest proportion of ACE-I (n = 433, 411, and 379, respectively) and DPP-IV (n = 556, 544, and 596, respectively) inhibitory peptides. LBPs with favorable pharmacokinetics and gastrointestinal stability tightly interacted with the active sites of ACE-I (-5.6 to -8.9 kcal/mol) and DPP-IV (-5.4 to -7.6 kcal/mol). Papain generated the most bioavailable LBPs (n = 459) with ACE-I (n = 223) and DPP-IV (n = 412) inhibitory activity. These peptides were non-toxic and gastrointestinal digestion stable. Notably, papain-based hydrolysis released some LBPs (n = 270) that inhibited both ACE-I and DPP-IV. Plant protease-based hydrolysis is a promising approach for producing lupin hydrolysates with ACE-I and DPP-IV inhibitory activities.

Defatted Wheat Germ Protein-Derived Peptides Showed Multiple Biological Activities from the Stomach to Small Intestine: In Silico and In Vitro Approaches

This study aimed to test the hypothesis that bioactive peptides can exert multiple bioactivities at different sites in the gastrointestinal tract. Our previous research identified 33 gastric-resistant peptides derived from wheat germ with potential antiadhesive activity against Helicobacter pylori in the stomach. In this work, in silico digestion of these peptides with trypsin, thermolysin, and chymotrypsin produced 67 peptide fragments. Molecular docking was conducted to predict their ACE and DPP-IV inhibitory activities in the small intestine. Three peptides (VPIPNPSGDR, VPY, and AR) were selected and synthesized for in vitro validation. Their generation in the gastrointestinal tract was verified via in vitro digestion, followed by mass spectrometry analysis. The IC50 values for ACE inhibition were 199.5 μM (VPIPNPSGDR), 316.3 μM (VPY), and 446.7 μM (AR). For DPP-IV inhibition, their IC50 values were 0.5, 1.6, and 4.0 mM, respectively. This research pioneers new directions in the emerging field of multifunctional peptides, providing scientific evidence to support the utilization of wheat germ as value-added food ingredients.

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.

Identification and Characterization of LBD Gene Family in Pseudoroegneria libanotica Reveals Functions of PseLBD1 and PseLBD12 in Response to Abiotic Stress

The lateral organ boundaries domain (LBD) plays a vital role as a transcriptional coactivator within plants, serving as an indispensable function in growth, development, and stress response. In a previous study, we found that the LBD genes of Pseudoroegneria libanotica (a maternal donor for three-quarter of perennial Triticeae species with good stress resistance, holds great significance in exploring its response mechanisms to abiotic stress for the Triticeae tribe) might be involved in responding to drought stress. Therefore, we further identified the LBD gene family in this study. A total of 29 PseLBDs were identified. Among them, 24 were categorized into subclass I, while 5 fell into subclass II. The identification of cis-acting elements reveals the extensive involvement of PseLBDs in various biological processes in P. libanotica. Collinearity analysis indicates that 86% of PseLBDs were single-copy genes and have undergone a single whole-genome duplication event. Transcriptomic differential expression analysis of PseLBDs under drought stress reveals that the most likely candidates for responding to abiotic stress were PseLBD1 and PseLBD12. They have been demonstrated to respond to drought, salt, heavy metal, and heat stress in yeast. Furthermore, it is plausible that functional divergence might have occurred among their orthologous genes in wheat. This study not only establishes a foundation for a deeper understanding of the biological roles of PseLBDs in P. libanotica but also unveils novel potential genes for enhancing the genetic background of crops within Triticeae crops, such as wheat.

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.

Advanced review on type II collagen and peptide: preparation, functional activities and food industry application

Type II collagen is a homologous super-helical structure consisting of three identical α1(II) chains. It is a major component of animal cartilage, and is widely used in the food industry. Type II collagen can be extracted by acids, salts, enzymes, and via auxiliary methods and can be further hydrolyzed chemically and enzymatically to produce collagen peptides. Recent studies have shown that type II collagen and its polypeptides have good self-assembly properties and important biological activities, such as maintaining cartilage tissue integrity, inducing immune tolerance, stimulating chondrocyte growth and redifferentiation, and providing antioxidant benefits. This review focuses specifically on type II collagen and describes its structure, extraction, and purification, as well as the preparation of type II collagen peptides. In particular, the self-assembly properties and functional activities of type II collagen and collagen peptides are reviewed. In addition, recent research advances in the application of type II collagen and collagen peptides in functional foods, food additives, food coating materials, edible films, and carriers for the food industry are presented. This paper provides more detailed and comprehensive information on type II collagen and peptide for their application.

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.

The biological role of prolyl oligopeptidase and the procognitive potential of its peptidic inhibitors from food proteins

Prolyl oligopeptidase (POP) is a conserved serine protease belonging to proline-specific peptidases. It has both enzymatic and non-enzymatic activity and is involved in numerous biological processes in the human body, playing a role in e.g., cellular growth and differentiation, inflammation, as well as the development of some neurodegenerative and neuropsychiatric disorders. This article describes the physiological and pathological aspects of POP activity and the state-of-art of its peptidic inhibitors originating from food proteins, with a particular focus on their potential as cognition-enhancing agents. Although some milk, meat, fish, and plant protein-derived peptides have the potential to be applied as natural, procognitive nutraceuticals, their effectiveness requires further evaluation, especially in clinical trials. We demonstrated that the important features of the most promising POP-inhibiting peptides are very short sequence, high content of hydrophobic amino acids, and usually the presence of proline residue.

Identification of Bioactive Peptides from a Laminaria digitata Protein Hydrolysate Using In Silico and In Vitro Methods to Identify Angiotensin-1-Converting Enzyme (ACE-1) Inhibitory Peptides

Bioactive peptides range in size from 2-30 amino acids and may be derived from any protein-containing biomass using hydrolysis, fermentation or high-pressure processing. Pro-peptides or cryptides result in shorter peptide sequences following digestion and may have enhanced bioactivity. Previously, we identified a protein hydrolysate generated from Laminaria digitata that inhibited ACE-1 in vitro and had an ACE-1 IC50 value of 590 µg/mL compared to an ACE-1 IC50 value of 500 µg/mL (~2.3 µM) observed for the anti-hypertensive drug Captopril©. A number of peptide sequences (130 in total) were identified using mass spectrometry from a 3 kDa permeate of this hydrolysate. Predicted bioactivities for these peptides were determined using an in silico strategy previously published by this group utilizing available databases including Expasy peptide cutter, BIOPEP and Peptide Ranker. Peptide sequences YIGNNPAKGGLF and IGNNPAKGGLF had Peptide Ranker scores of 0.81 and 0.80, respectively, and were chemically synthesized. Synthesized peptides were evaluated for ACE-1 inhibitory activity in vitro and were found to inhibit ACE-1 by 80 ± 8% and 91 ± 16%, respectively. The observed ACE-1 IC50 values for IGNNPAKGGLF and YIGNNPAKGGLF were determined as 174.4 µg/mL and 133.1 µg/mL. Both peptides produced sequences following simulated digestion with the potential to inhibit Dipeptidyl peptidase IV (DPP-IV).

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.

In Silico Prospecting for Novel Bioactive Peptides from Seafoods: A Case Study on Pacific Oyster (Crassostrea gigas)

Pacific oyster (Crassostrea gigas), an abundant bivalve consumed across the Pacific, is known to possess a wide range of bioactivities. While there has been some work on its bioactive hydrolysates, the discovery of bioactive peptides (BAPs) remains limited due to the resource-intensive nature of the existing discovery pipeline. To overcome this constraint, in silico-based prospecting is employed to accelerate BAP discovery. Major oyster proteins were digested virtually under a simulated gastrointestinal condition to generate virtual peptide products that were screened against existing databases for peptide bioactivities, toxicity, bitterness, stability in the intestine and in the blood, and novelty. Five peptide candidates were shortlisted showing antidiabetic, anti-inflammatory, antihypertensive, antimicrobial, and anticancer potential. By employing this approach, oyster BAPs were identified at a faster rate, with a wider applicability reach. With the growing market for peptide-based nutraceuticals, this provides an efficient workflow for candidate scouting and end-use investigation for targeted functional product preparation.

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.

Identification, Screening, and Comprehensive Evaluation of Novel DPP-IV Inhibitory Peptides from the Tilapia Skin Gelatin Hydrolysate Produced Using Ginger Protease

PURPOSE

Inhibition of dipeptidyl peptidase-IV (DPP-IV) is an effective therapy for treating type II diabetes (T2D) that has been widely applied in clinical practice. We aimed to evaluate the DPP-IV inhibitory properties of ginger protease hydrolysate (GPH) and propose a comprehensive approach to screen and evaluate DPP-IV inhibitors.

METHODS

We evaluated the in vitro inhibitory properties of fish skin gelatin hydrolysates produced by five proteases, namely, neutral protease, alkaline protease, bromelain, papain, and ginger protease, toward DPP-IV. We screened the most potent DPP-IV inhibitory peptide (DIP) using liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with in silico analysis. Next, surface plasmon resonance (SPR) technology was innovatively introduced to explore the interactions between DPP-IV and DIP, as well as the IC₅₀. Furthermore, we performed oral administration of DIP in rats to study its in vivo absorption.

RESULTS

GPH displayed the highest degree of hydrolysis (20.37%) and DPP-IV inhibitory activity (65.18%). A total of 292 peptides from the GPH were identified using LC-MS/MS combined with de novo sequencing. Gly-Pro-Hyp-Gly-Pro-Pro-Gly-Pro-Gly-Pro (GPXGPPGPGP) was identified as the most potent DPP-IV inhibitory peptide after in silico screening (Peptide Ranker and molecular docking). Then, the in vitro study revealed that GPXGPPGPGP had a high inhibitory effect on DPP-IV (IC₅₀: 1012.3 ± 23.3 μM) and exhibited fast kinetics with rapid binding and dissociation with DPP-IV. In vivo analysis indicated that GPXGPPGPGP was not absorbed intact but partially, in the form of dipeptides and tripeptides.

CONCLUSION

Overall, the results suggested that GPH would be a natural functional food for treating T2D and provided new ideas for searching and evaluating potential antidiabetic compounds. The obtained GPXGPPGPGP can be structurally optimized for in-depth evaluation in animal and cellular experiments.

Identification of Bioactive Peptides from Nannochloropsis oculata Using a Combination of Enzymatic Treatment, in Silico Analysis and Chemical Synthesis

In vitro ACE-1 inhibitory peptides were characterised previously from a number of microalgal species including Spirulina platensis (peptide IAPG), Chlorella vulgaris (peptides FDL, AFL, VVPPA), Isochrysis galbana (peptide YMGLDLK), Chlorella sorokiniana (peptides IW and LW) and indeed Nannochloropsis oculata (peptides GMNNLTP and LEQ). The isolation of protein from Nannochloropsis oculata using a combination of ammonium salt precipitation and xylanase treatment of resulting biomass combined with molecular weight cut off filtration to produce a permeate and characterisation of bioactive peptides is described. The Angiotensin-1-converting enzyme (ACE-1) IC₅₀ value for the generated permeate fraction was 370 µg/mL. Ninety-five peptide sequences within the permeate fraction were determined using mass spectrometry and eight peptides were selected for chemical synthesis based on in silico analysis. Synthesized peptides were novel based on a search of the literature and relevant databases. In silico, simulated gastrointestinal digestion identified further peptides with bioactivities including ACE-1 inhibitory peptides and peptides with antithrombotic and calcium/calmodulin-dependent kinase II (CAMKII) inhibition. This work highlights the potential of Nannochloropsis oculata biomass as both a protein and bioactive peptide resource, which could be harnessed for use in the development of functional foods and feeds.

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.

Bioactive peptides from meat: Current status on production, biological activity, safety, and regulatory framework

By-products of the meat processing industry which are often discarded as waste are excellent protein substrates for producing bioactive peptides through enzymatic hydrolysis. These peptides have tremendous potential for the development of functional food products but there is scanty information about the regulations on bioactive peptides or products in various parts of the world. This review focuses on the diverse bioactive peptides identified from different meat and meat by-products, their bioactivity and challenges associated in their production as well as factors limiting their effective commercialization. Furthermore, this report provides additional information on the possible toxic peptides formed during production of the bioactive peptides, which enables delineation of associated safety and risk. The regulatory framework in place for bioactive peptide-based foods in different jurisdictions and the future research directions are also discussed. Uniform quality, high cost, poor sensory acceptance, lack of toxicological studies and clinical evidence, paltry stability, and lack of bioavailability data are some of the key challenges hindering commercial advancement of bioactive peptide-based functional foods. Absorption, distribution, metabolism and excretion (ADME) studies in rodents, in vitro genotoxicity, and immunogenicity data could be considered as absolute pre-requisites to ensure safety of bioactive peptides. In the absence of ADME and genotoxicity data, long term usage to evaluate safety is highly warranted. Differences in legislations among countries pose challenge in the international trade of bioactive peptides-based functional foods. Harmonization of regulations could be a way out and hence further research in this area is encouraged.

Proteomics Characterization of Food-Derived Bioactive Peptides with Anti-Allergic and Anti-Inflammatory Properties

Bioactive peptides are found in foods and dietary supplements and are responsible for health benefits with applications in human and animal medicine. The health benefits include antihypertensive, antimicrobial, antithrombotic, immunomodulatory, opioid, antioxidant, anti-allergic and anti-inflammatory functions. Bioactive peptides can be obtained by microbial action, mainly by the gastrointestinal microbiota from proteins present in food, originating from either vegetable or animal matter or by the action of different gastrointestinal proteases. Proteomics can play an important role in the identification of bioactive peptides. High-resolution mass spectrometry is the principal technique used to detect and identify different types of analytes present in complex mixtures, even when available at low concentrations. Moreover, proteomics may provide the characterization of epitopes to develop new food allergy vaccines and the use of immunomodulating peptides to induce oral tolerance toward offending food allergens or even to prevent allergic sensitization. In addition, food-derived bioactive peptides have been investigated for their anti-inflammatory properties to provide safer alternatives to nonsteroidal anti-inflammatory drugs (NSAIDs). All these bioactive peptides can be a potential source of novel drugs and ingredients in food and pharmaceuticals. The following review is focused on food-derived bioactive peptides with antiallergic and anti-inflammatory properties and summarizes the new insights into the use of proteomics for their identification and quantification.

In Silico Analysis of Bioactive Peptides Produced from Underutilized Sea Cucumber By-Products-A Bioinformatics Approach

Bioinformatic tools are widely used in predicting potent bioactive peptides from food derived materials. This study was focused on utilizing sea cucumber processing by-products for generating antioxidant and ACE inhibitory peptides by application of a range of in silico techniques. Identified peptides using LC-MS/MS were virtually screened by PepRank technique followed by in silico proteolysis simulation with representative digestive enzymes using BIOPEP-UWMTM data base tool. The resultant peptides after simulated digestion were evaluated for their toxicity using ToxinPred software. All digestive resistance peptides were found to be non-toxic and displayed favorable functional properties indicating their potential for use in a wide range of food applications, including hydrophobic and hydrophilic systems. Identified peptides were further assessed for their medicinal characteristics by employing SwissADME web-based application. Our findings provide an insight on potential use of undervalued sea cucumber processing discards for functional food product development and natural pharmaceutical ingredients attributed to the oral drug discovery process.

Dipeptidyl Peptidase IV Inhibitory Peptides Generated in Dry-Cured Pork Loin during Aging and Gastrointestinal Digestion

The ability of peptides from an aqueous and salt-soluble protein extract of dry-cured pork loins to inhibit the action of dipeptidyl peptidase IV was determined. This activity was assessed at different times of the production process, i.e., 28, 90, 180, 270 and 360 days. The resistance of the biological property during the simulated digestive process was also assessed. For this, the extracts were hydrolyzed with pepsin and pancreatin as a simulated digestion step of the gastrointestinal tract and fractionated (>7 kDa) as an intestinal absorption step. The results indicate that dried-pork-loin peptides may have potential as functional food ingredients in the prevention and treatment of type 2 diabetes mellitus. In particular, the APPPPAEV, APPPPAEVH, KLPPLPL, RLPLLP, VATPPPPPPK, VPIPVPLPM and VPLPVPVPI sequences show promise as natural food compounds helpful in maintaining good health.

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.

Bioinformatics and Computer Simulation approaches to the discovery and analysis of Bioactive Peptides

The traditional process of separating and purifying bioactive peptides is laborious and time-consuming. Using a traditional process to identify is difficult, and there is a lack of fast and accurate activity evaluation methods. How to extract bioactive peptides quickly and efficiently is still the focus of bioactive peptides research. In order to improve the present situation of the research, bioinformatics techniques and peptidome methods are widely used in this field. At the same time, bioactive peptides have their own specific pharmacokinetic characteristics, so computer simulation methods have incomparable advantages in studying the pharmacokinetics and pharmacokinetic-pharmacodynamic correlation models of bioactive peptides. The purpose of this review is to summarize the combined applications of bioinformatics and computer simulation methods in the study of bioactive peptides, with focuses on the role of bioinformatics in simulating the selection of enzymatic hydrolysis and precursor proteins, activity prediction, molecular docking, physicochemical properties, and molecular dynamics. Our review shows that new bioactive peptide molecular sequences with high activity can be obtained by computer-aided design. The significance of the pharmacokinetic-pharmacodynamic correlation model in the study of bioactive peptides is emphasized. Finally, some problems and future development potential of bioactive peptides binding new technologies are prospected.

A Novel Insight into Screening for Antioxidant Peptides from Hazelnut Protein: Based on the Properties of Amino Acid Residues

This study used the properties of amino acid residues to screen antioxidant peptides from hazelnut protein. It was confirmed that the type and position of amino acid residues, grand average of hydropathy, and molecular weight of a peptide could be comprehensively applied to obtain desirable antioxidants after analyzing the information of synthesized dipeptides and BIOPEP database. As a result, six peptides, FSEY, QIESW, SEGFEW, IDLGTTY, GEGFFEM, and NLNQCQRYM were identified from hazelnut protein hydrolysates with higher antioxidant capacity than reduced Glutathione (GSH) against linoleic acid oxidation. The peptides having Tyr residue at C-terminal were found to prohibit the oxidation of linoleic acid better than others. Among them, peptide FSEY inhibited the rancidity of hazelnut oil very well in an oil-in-water emulsion. Additionally, quantum chemical parameters proved Tyr-residue to act as the active site of FSEY are responsible for its antioxidation. This is the first presentation of a novel approach to excavating desired antioxidant peptides against lipid oxidation from hazelnut protein via the properties of amino acid residues.

Trends in In Silico Approaches to the Prediction of Biologically Active Peptides in Meat and Meat Products as an Important Factor for Preventing Food-Related Chronic Diseases

The increasing awareness of modern consumers regarding the nutritional and health value of food has changed their preferences, as well their requirements, for food products, including meat and meat products. Expanding the knowledge on the impact of food on human health is currently one of the most important research areas for scientists worldwide, and it is also of interest to consumers who want to consciously compose their daily diets. New research methods, such as in silico techniques, offer solutions to these new challenges. These research methods are preferred over food evaluation, e.g., from meat, because of their advantages, such as low costs, shorter analysis times, and general availability (e.g., online databases), and are often used to design in vitro and, subsequently, in vivo tests. This review focuses on the possible use of in silico computerized methods to assess the potential of food as a source of these health-relevant biomolecules by using examples from the literature on meat and meat products. This review also provides information and important suggestions for analyzing peptides in terms of assessing their best sources, and screening those resistant to digestive factors and that show biological activity. The information provided in this review could contribute to the development of new sources of foods as biomolecules important for preventing or treating food-related chronic diseases, such as obesity, hypertension, and diabetes.

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.

The physiological activity of bioactive peptides obtained from meat and meat by-products

Meat and meat products constitute an important source of nutrients and play vital roles for growth, maintenance and repair of the body. In addition to the high quality of proteins, meat is also regarded as a major resource to produce bioactive peptides. Meat processing industry also produces by-products such as bones, blood and viscera, which could be further used for the production of bioactive compounds. In the physiological analysis, meat bioactive peptides have been reported to exert antioxidant, anti-hypertensive, anti-inflammatory, anti-microbial and antitumoral activities, which endow nutritional and functional value of meat. With the objective to exert the functional effect, the bioavailability should also be considered due to the degradation by digestion enzymes and the absorption process in intestinal mucosa. In this chapter, the general source, the enzymatic hydrolysis, the physiological effects as well as the bioavailability of bioactive peptides in meat are discussed.

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.

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.

Cryptic Host Defense Peptides: Multifaceted Activity and Prospects for Medicinal Chemistry

Host defense peptides (HDPs) comprise a heterogeneous group of evolutionarily conserved and biologically active small molecules that are produced by different organisms. HDPs are widely researched because they often have multiple biological activities, for example antimicrobial, immunomodulatory and anticancer activity. In this context, in this review we focus on cryptic HDPs, molecules derived specifically from proteolytic processing of endogenous precursor proteins. Here, we explore the biological activity of such molecules and we further discuss the development of optimized sequences based on these natural cryptic HDPs. In addition, we present clinical-phase studies of cryptic HDPs (natural or optimized), and point out the possible applicability of these molecules in medicinal chemistry.

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.

An overview on antioxidant peptides from rice bran proteins: extraction, identification, and applications

Rice by-products, generated through the milling processes, have recently been recognized as a potential source of bioactive compounds, such as proteins, essential amino acids, and phenolics. Owing to their antioxidant capacity (which improve the storage stability of foods), these compounds have gained much attention because of their beneficial impacts on human health. It has to be noted that large quantities of rice by-products are not efficiently utilized, which may result in industrial wastes and environmental consequences. Thence, the aim of this review is to provide a comprehensive insight on the antioxidant capabilities, extraction, identification, functional attributes, and applications of bioactive hydrolysates and peptides derived from rice bran protein. This overview would provide an insight on rice bran proteins, which are abundant in bioactive peptides, and could be used as value-added products in food and pharmaceutical applications. Inclusion of bioactive peptides to prevent food spoilage while maintaining food safety has also been highlighted.

The identification and characterisation of novel bioactive peptides derived from porcine liver

Bioactive peptides (BAPs) can be derived from a variety of sources; these could be from dietary proteins which are then broken down in the gastrointestinal tract to release BAPs, or they can be isolated from various sources ex vivo. Sources include plant-based proteins such as soy, and chickpeas, and animal proteins from waste from the meat industry and from fish skin. Bioinformatics is also a useful approach to assess the peptides released from digests due to the great number of possible sequences that can be isolated from proteins. Therefore, an in silico analysis of peptides could potentially lead to a more rapid discovery of BAPs. This article investigates a "crude" liver peptide mixture derived from papain hydrolysis of porcine liver and purified peptides derived from the hydrolysates following HPLC fractionation and in silico digestion of the host proteins identified using LC-MS/MS. This allowed the identification of two proteins (cytosol aminopeptidase and haemoglobin subunit alpha) present in the "crude" mixture after LC-MS/MS. In silico hydrolysis of these proteins identified that several peptides were predicted to be both present in the crude mixture using the BIOPEP database and to have potential bioactivity using the Peptide Ranker tool. Peptides (FWG, MFLG and SDPPLVFVG) with the greatest potential bioactivity and which had not previously been reported in the literature were then synthesised. The results indicated that the predicted bioactivity of the synthetic peptides would likely include antioxidant activity. FWG and MFLG derived from the in silico papain hydrolysis of cytosol aminopeptidase showed activity better or comparable to Trolox in the Oxygen Radical Absorbance Capacity (ORAC) assay. The use of these in silico tools, alongside a robust range of biochemical assays which cover a wider range of bioactivities would be a way of improving the discovery of novel bioactive peptides.

In silico Design of a Multivalent Vaccine Against Candida albicans

Invasive candidiasis (IC) is the most common nosocomial infection and a leading cause of mycoses-related deaths. High-systemic toxicity and emergence of antifungal-resistant species warrant the development of newer preventive approaches against IC. Here, we have adopted an immunotherapeutic peptide vaccine-based approach, to enhance the body's immune response against invasive candida infections. Using computational tools, we screened the entire candida proteome (6030 proteins) and identified the most immunodominant HLA class I, HLA class II and B- cell epitopes. By further immunoinformatic analyses for enhanced vaccine efficacy, we selected the 18- most promising epitopes, which were joined together using molecular linkers to create a multivalent recombinant protein against Candida albicans (mvPC). To increase mvPC's immunogenicity, we added a synthetic adjuvant (RS09) to the mvPC design. The selected mvPC epitopes are homologous against all currently available annotated reference sequences of 22 C. albicans strains, thus offering a higher coverage and greater protective response. A major advantage of the current vaccine approach is mvPC's multivalent nature (recognizing multiple-epitopes), which is likely to provide enhanced protection against complex candida antigens. Here, we describe the computational analyses leading to mvPC design.

A multi-approach peptidomic analysis of hen egg white reveals novel putative bioactive molecules

Chicken egg white is a raw material broadly used as additive for the preparation of food and cosmetoceutical products. To describe its molecular properties, various proteomic investigations were performed in the last decade characterizing highly abundant components. No peptidomic counterparts were accomplished so far; scientific literature only reports on the characterization of specific bioactive peptides or preparations from egg white and its hydrolysates, which was performed through dedicated functional assays. In this study, a broad description of the egg white peptidome at 24, 336 and 672 h after laying was achieved using three peptide extraction procedures, which were combined with MALDI-TOF-TOF-MS and nanoLC-ESI-Q-Orbitrap-MS/MS analyses. In the whole, 506 peptides were characterized; they mostly resulted from the physiological degradation of intact proteins following the activity of endoprotease ArgC-, trypsin- and plasmin-like enzymes. Eventual detection of peptide post-translational modifications also provided structural information on parental proteins. When analyzed by bioinformatics and/or compared with literature data, identified peptides allowed recognizing a number of protein fragments associated with different hypothetical biological activities. These results confirmed previous observations regarding functional characteristics of egg white unfractionated preparations or purified molecules, emphasizing the useful application of this raw material in human nutrition and cosmetics. Finally, a comparative label-free peptidomic evaluation of samples stored for different times under refrigeration identified 31 peptides showing significant quantitative changes during storage. BIOLOGICAL SIGNIFICANCE: This study provided the largest inventory of peptides described in chicken egg while so far. In addition, it identified a number of protein fragments associated with hypothetical antihypertensive, antioxidant, antiinflammatory, antimicrobial, anticancer, antiviral, antibiofilm, calcium-binding, antidiabetic, antithrombotic, adipogenic differentiating, stimulating/immunostimulating, hormonal, lipid-binding and cell adhesion-affecting activities. These results confirmed previous observations regarding functional characteristics of egg white unfractionated preparations or purified molecules, emphasizing the useful application of this raw material in human nutrition and cosmetics.

Structure-activity relationships study on biological activity of peptides as dipeptidyl peptidase IV inhibitors by chemometric modeling

The aim of this study is to identify the potential descriptors affecting the inhibitory activity of the peptides inhibiting dipeptidyl peptidase IV (DPP-IV). This study provides important information for assessing the biological activity of the new peptide sequences of food origin or making structural modifications to the current inhibitors to improve their performance. For this purpose, the chemometric method describing the relationship between the structure of food peptides and their biological activity (structure-activity relationship [SAR]) was used to theoretically predict the potential of bioactivity of peptides. Data on the physicochemical properties of amino acids in the dipeptides acting as inhibitors of DPP-IV were collected and analyzed for using these properties as descriptors in further analysis. A total of 252 dipeptide sequences with confirmed DPP-IV inhibitory activity available in the BIOPEP-UWM database were included in the analysis, and 16 descriptors defining individual amino acids (such as molecular weight, polarity, hydropathicity, bulkiness, buried residue, and acceptable and normalized frequency of alpha-helix and beta-sheet) were identified. Based on this information, a data matrix was constructed and used in the chemometric analysis (principal component analysis and multiple linear regression). From the SAR model created, a multiple regression equation was derived to predict the biological activity of the dipeptide DPP-IV inhibitors.

Discovery of hPRDX5-based peptide inhibitors blocking PD-1/PD-L1 interaction through in silico proteolysis and rational design

PURPOSE

The human peroxiredoxin-5 (hPRDX5) is a member of the family of antioxidant enzymes, which could resist immunosuppression by promoting immune organs development, lymphocyte proliferation and up-regulation of the levels of serum cytokines. However, being a recombinant protein, the hPRDX5 exhibits some problems including the high production cost and bad tissue penetration. Compared to macromolecular therapeutic agents, synthetic peptides have several advantages as drug candidates, such as lower manufacturing costs, reduced immunogenicity, and better organ or tumor penetration. The purpose of this research was to design the novel peptides come from hPRDX5 that can block the interaction of PD-1 and PD-L1.

METHODS

Herein in this work, we firstly confirmed the inhibitory activity of hPRDX5 on the binding of PD-L1 to PD-1 based on the previous observation, subsequently, in silico proteolysis and rational design (such as alanine scanning mutagenesis and truncation) were used to automate the design of new peptides derived from hPRDX5 with anti-tumour activity.

RESULTS

We found that the most potent peptide could block the PD-1/PD-L1 interaction effectively with an IC₅₀ of 0.646 μM, and could restore the function of Jurkat T cells which had been suppressed by stimulated HCT116 cells. Moreover, experiments with tumor-bearing mice models showed that the peptide IMB-P6-10 could effectively inhibit tumor growth and showed extraordinary low acute toxicity in vivo.

CONCLUSIONS

The peptides described in this paper may provide novel low-molecular-weight drug candidates for cancer immunotherapy.

Gene synthesizing, expression and immunogenicity characterization of recombinant translation elongation factor 2 from Dermatophagoides farinae

House dust mite (HDM) hypersensitivity increasingly affects millions of individuals worldwide. Although numerous major allergens produced by HDM species have been characterized, some of the less potent allergens remain to be studied. The present study aimed to obtain the recombinant allergen of Translation Elongation Factor 2 (TEF 2) from the HDM Dermatophagoides farinae by synthesizing, and then expressing the recombinant TEF 2 to identify its immunogenicity. In the present study, the D. farinae TEF 2 (Der f TEF 2) was synthesized, expressed and purified. The molecular characteristics of Der f TEF 2 were analyzed using bioinformatics approaches. The recombinant protein was purified via affinity chromatography, and the allergenicity was assessed using immunoblotting, ELISAs and skin prick tests. The gene for TEF 2 consists of 2,535 bp and encodes an 844‑amino acid protein. A positive response to recombinant Der f TEF 2 was detected in 16.2% of 37 patients with HDM allergies using skin prick tests. In addition, the immunoblotting indicated that the protein showed a high ability to bind serum IgE from patients allergic to HDMs, and that the recombinant TEF 2 was highly immunogenic. Bioinformatics analysis predicted 17 peptides as B cell epitopes (amino acids 29‑35, 55‑64, 92‑99, 173‑200, 259‑272, 311‑318, 360‑365, 388‑395, 422‑428, 496‑502, 512‑518, 567‑572, 580‑586, 602‑617, 785‑790, 811‑817 and 827‑836) and 14 peptides as T cell epitopes (amino acids 1‑15, 65‑79, 120‑134, 144‑159, 236‑250, 275‑289, 404‑418, 426‑440, 463‑477, 510‑524, 644‑658, 684‑698, 716‑730 and 816‑830). The software DNAStar predicted the secondary structure of TEF 2, and showed that 27 α‑helices and five β‑sheets were found in the protein. In conclusion, the present study cloned and expressed the Der f TEF 2 gene, and the recombinant protein exhibited immunogenicity, providing a theoretical bases, and references, for the diagnosis and treatment of allergic disease.