Harnessing the Therapeutic Potential of Peptides for Synergistic Treatment of Alzheimer's Disease by Targeting Aβ Aggregation, Metal-Mediated Aβ Aggregation, Cholinesterase, Tau Degradation, and Oxidative Stress

Alzheimer's disease (AD) is a progressive multifaceted neurodegenerative disease and remains a formidable global health challenge. The current medication for AD gives symptomatic relief and, thus, urges us to look for alternative disease-modifying therapies based on a multitarget directed approach. Looking at the remarkable progress made in peptide drug development in the last decade and the benefits associated with peptides, they offer valuable chemotypes [multitarget directed ligands (MTDLs)] as AD therapeutics. This review recapitulates the current developments made in harnessing peptides as MTDLs in combating AD by targeting multiple key pathways involved in the disease's progression. The peptides hold immense potential and represent a convincing avenue in the pursuit of novel AD therapeutics. While hurdles remain, ongoing research offers hope that peptides may eventually provide a multifaceted approach to combat AD.

Effects of walnut seed coat polyphenols on walnut protein hydrolysates: Structural alterations, hydrolysis efficiency, and acetylcholinesterase inhibitory capacity

The walnut meal is rich in nutrients such as protein from the kernel and polyphenolic compounds from the seed coat. However, the influences of seed coat polyphenols on walnut protein (WP) hydrolysis remained unclear. In this study, our findings indicated that polyphenols induced alterations in the secondary structure and amino acid composition of WP. These changes resulted in both a hindrance of hydrolysis and an enhancement of acetylcholinesterase (AChE) inhibition. Furthermore, four peptides of 119 identified peptides (LR, SF, FQ, and FR) were synthesized based on higher predicted bioactivity and Vinascores in silico. Among them, FQ showed interaction with amino acid residues in AChE through the formation of four π-π stacking bonds and two hydrogen bonds, resulting in the highest AChE inhibitory capacity. The combination index showed that chlorogenic acid derived from the seed coat and FQ at the molar ratio of 1:4 exhibited synergistic effects of AChE inhibition.

Identification novel salt-enhancing peptides from largemouth bass and exploration their action mechanism with transmembrane channel-like 4 (TMC4) by molecular simulation

The purpose of this study was to screen and verify salt-enhancing peptides that can effectively reduce sodium consumption from Largemouth bass myosin through virtual hydrolysis, molecular simulation, and sensory evaluation. The human transmembrane channel-like 4 (TMC4) was constructed using Alphafold2, with 93.3 % of amino acids falling within allowed regions. A total of 19 peptides were predicted through virtual hydrolysis and screening. DAF, QIF, RPAL, and IPVM significantly enhanced the saltiness perception, and QIF exhibited the most pronounced effect in enhancing saltiness (P < 0.05). The residues Ala258, Ser546, Ser603, Phe259, Cys265, Glu539, Lys278 and Ser585 were identified as key binding sites. The TMC4-DAF complex achieved stability after 20, 000 ps, exhibiting an average RMSD value of 0.84 nm. DAF consistently displayed fluctuations at approximately 3.05 nm, and the number of hydrogen bonds varied between 3 and 5. These results suggested that Alphafold2 modelling can be used for predicting salt-enhancing peptides.

Food-derived Peptides as Promising Neuroprotective Agents: Mechanism and Therapeutic Potential

Many food-derived peptides have the potential to improve brain health and slow down neurodegeneration. Peptides are produced by the enzymatic hydrolysis of proteins from different food sources. These peptides have been shown to be involved in antioxidant and anti-inflammatory activity, neuro-transmission modulation, and gene expression regulation. Although few peptides directly affect chromatin remodeling and histone alterations, others indirectly affect the neuroprotection process by interfering with epigenetic changes. Fish-derived peptides have shown neuroprotective properties that reduce oxidative stress and improve motor dysfunction in Parkinson's disease models. Peptides from milk and eggs have been found to have anti-inflammatory properties that reduce inflammation and improve cognitive function in Alzheimer's disease models. These peptides are potential therapeutics for neurodegenerative diseases, but more study is required to assess their efficacy and the underlying neuroprotective benefits. Consequently, this review concentrated on each mechanism of action used by food-derived peptides that have neuroprotective advantages and applications in treating neurodegenerative diseases. This article highlights various pathways, such as inflammatory pathways, major oxidant pathways, apoptotic pathways, neurotransmitter modulation, and gene regulation through which food-derived peptides interact at the cellular level.

Food-Derived Peptides: Beneficial CNS Effects and Cross-BBB Transmission Strategies

Food-derived peptides, as dietary supplements, have significant effects on promoting brain health and relieving central nervous system (CNS) diseases. However, the blood-brain barrier (BBB) greatly limits their in-brain bioavailability. Thus, overcoming the BBB to target the CNS is a major challenge for bioactive peptides in the prevention and treatment of CNS diseases. This review discusses improvement in the neuroprotective function of food-derived active peptides in CNS diseases, as well as the source of BBB penetrating peptides (BBB-shuttles) and the mechanism of transmembrane transport. Notably, this review also discusses various peptide modification methods to overcome the low permeability and stability of the BBB. Lipification, glycosylation, introduction of disulfide bonds, and cyclization are effective strategies for improving the penetration efficiency of peptides through the BBB. This review provides a new prospective for improving their neuroprotective function and developing treatments to delay or even prevent CNS diseases.

Virtual screening and structure optimization of xanthine oxidase inhibitory peptides from whole protein sequences of Pacific white shrimp via molecular docking

Xanthine oxidase (XO) inhibitory peptides are safer than conventional pharmacological therapy in relieving hyperuricemia. However, traditional enzymatic hydrolysis, separation, and purification techniques for bio-active peptide preparation are time-consuming, inefficient, and labor-intensive. In this study, molecular docking and BLAST were used to virtually screen XO inhibitory peptides from whole protein sequences of Pacific white shrimp according to the bio-active peptides database, and the structure of peptides was optimized based on the structure-effective relationship. Seven new XO inhibitory peptides were virtual screened rapidly from Pacific white shrimp, and YNITGW (IC50 = 9.78 ± 0.13 mM) showed the strongest activity. The results of YNITGW optimization showed that the insertion of Trp residue in the middle position of peptides could effectively enhance the activity. This study revealed that screening and optimizing peptides by molecular docking were a novel and feasible method to obtain bio-active peptides.

Noncovalent Interaction of Lactoferrin with Epicatechin and Epigallocatechin: Focus on Fluorescence Quenching and Antioxidant Properties

Lactoferrin (LF) from bovine milk possesses antioxidant activity, immune regulatory and other biological activities. However, the effects of epicatechin (EC) and epigallocatechin (EGC) interacting with LF on the antioxidant activity of LF have not been investigated. Therefore, this study aimed to explore their interaction mechanism and the antioxidant activity of LF. UV spectra revealed that EGC (100 μM) induced a higher blue shift of LF at the maximum absorption wavelength than that of EC (100 μM). Fluorescence spectra results suggested that LF fluorescence was quenched by EC and EGC in the static type, which changed the polarity of the microenvironment around LF. The quenching constants Ksv (5.91 × 103-9.20 × 103) of EC-LF complexes at different temperatures were all higher than that (1.35 × 103-1.75 × 103) of the EGC-LF complex. EC could bind to LF via hydrophobic interactions while hydrogen bonding and van der Waals forces drove the binding of EGC to LF. Both the EC-LF complex and EGC-LF complex could bind to LF with one site. EGC formed more hydrogen bonds with LF than that of EC. The antioxidant activity of LF was increased by the high addition level of EC and EGC. These findings would provide more references for developing LF-catechin complexes as functional antioxidants.

Modification of a Novel Umami Octapeptide with Trypsin Hydrolysis Sites via Homology Modeling and Molecular Docking

Increasing the copy number of peptides is an effective method to genetically engineer recombinant expression and obtain umami peptides in large quantities. However, the umami taste value of multicopy number umami peptides is lower than the single ones, thus limiting the industrial application of recombinantly expressed umami peptides. With aims to solve this problem, modification of an umami beefy meaty peptide (BMP) with trypsin hydrolysis sites was carried out via homology modeling and molecular docking in this study. A total of 1286 modified peptide sequences were created and molecularly simulated for docking with the homology modeling-constructed umami receptor (T1R1/T1R3), and 837 peptides were found to be better docked than the BMP. Afterward, the MLSEDEGK peptide with the highest docking score was synthesized. And umami taste evaluation results demonstrated that this modified peptide was close to that of monosodium glutamate (MSG) and BMP, as confirmed by electronic tongue and sensory evaluation (umami value: 8.1 ± 0.2 for BMP; 8.2 ± 0.3 for MLSEDEGK peptide). Meanwhile, mock trypsin digestion of eight copies of MLSEDEGK peptide results showed that the introduced digestion sites were effective. Therefore, the novel modified BMP in this study has the potential for large-scale production by genetic engineering.

Purification, identification and hypolipidemic activities of three novel hypolipidemic peptides from tea protein

In this study, hypolipidemic peptides were obtained from tea protein by enzymatic hydrolysis, ultrafiltration and high-performance liquid chromatography. Subsequently, the hypolipidemic peptides were identified by mass spectrometry and screened through molecular docking technology, and the hypolipidemic activities and mechanisms of the active peptides were explored. The results showed that the hydrolysate of hypolipidemic peptides obtained by pepsin hydrolysis for 3 h had good bile salt binding ability. After purification, identification and molecular docking screening, three novel hypolipidemic peptides FLF, IYF and QIF were obtained. FLF, IYF and QIF can interact with the receptor proteins 1LPB and 1F6W through hydrogen bonds, π-π bonds, hydrophobic interactions and van der Waals forces, thus exerting hypolipidemic activities. Activity studies showed that, compared with the positive controls, FLF, IYF and QIF had excellent sodium taurocholate binding abilities, pancreatic lipase inhibitory activities and cholesterol esterase inhibitory activities. Moreover, FLF, IYF and QIF can effectively inhibit lipogenic differentiation of 3T3-L1 preadipocytes, reduce intracellular lipid and low-density lipoprotein content and increase high-density lipoprotein content. These results indicated that the three novel hypolipidemic peptides screened in this study had excellent hypolipidemic activities and were expected to be used as natural-derived hypolipidemic active ingredients for the development and application in functional foods.

Preparation, identification, and molecular docking of novel elastase inhibitory peptide from walnut (Juglans regia L.) meal

This study aimed to isolate bioactive peptides with elastase inhibitory activity from walnut meal via ultrasonic enzymatic hydrolysis. The optimal hydrolysis conditions of walnut meal protein hydrolysates (WMPHs) were obtained by response surface methodology (RSM), while a molecular weight of<3 kDa fraction was analyzed by LC-MS/MS, and 556 peptides were identified. PyRx virtual screening and Autodock Vina molecular docking revealed that the pentapeptide Phe-Phe-Val-Pro-Phe (FFVPF) could interact with elastase primarily through hydrophobic interactions, hydrogen bonds, and π-sulfur bonds, with a binding energy of -5.22 kcal/mol. The verification results of inhibitory activity showed that FFVPF had better elastase inhibitory activity, with IC₅₀ values of 0.469 ± 0.01 mg/mL. Furthermore, FFVPF exhibited specific stability in the gastric environment. These findings suggest that the pentapeptide FFVPF from defatted walnut meal could serve as a potential source of elastase inhibitors in the food, medical, and cosmetics industries.

Arginine-Containing Peptides Derived from Walnut Protein Against Cognitive and Memory Impairment in Scopolamine-Induced Zebrafish: Design, Release, and Neuroprotection

The purpose of this study was to investigate the neuroprotective effect of Arg-containing peptides from walnut storage protein sequences in scopolamine-induced zebrafish and further to validate the potential neuroprotection of Arg-containing peptide enriched walnut hydrolysates prepared by in silico hydrolysis and controlled enzymatic release. Results showed that walnut derived Arg-containing peptides with high abundance and great bioactivity predicted by bioinformatics displayed potent neuroprotection in scopolamine-induced zebrafish, and regulation of neurotransmitter level and antioxidant enzyme activity might be the main target for Arg-containing peptides to exert neuroprotection. Notably, Arg-containing peptides (not free arginine) contributed greater neuroprotection, and the positive charge and cell-penetrating properties also affected their neuroprotection. Subsequently, Arg-containing peptides could be released efficiently from walnut protein following hydrolysis by trypsin, pepsin, papain, and thermolysin (bound arginine content: ranging from 110.43 ± 1.58 to 121.82 ± 1.02 mg/g). Among them, trypsin had excellent potential for releasing Arg-containing peptides in silico hydrolysis, and its hydrolysate was confirmed to have neuroprotective capacity, indicating that the combination of in silico hydrolysis and controlled enzymatic release might be an effective approach to obtain Arg-containing neuroprotective peptides.

Effects of low molecular weight peptides from monkfish (Lophius litulon) roe on immune response in immunosuppressed mice

This study aimed to investigate the immunomodulatory activation of low-molecular-weight peptides from monkfish (Lophius litulon) roe (named MRP) on cyclophosphamide (CTX)-induced immunosuppressed mice. Our results indicated that MRP (100 mg/kg/d BW) could significantly increase the body weight and immune organ index, and improve the morphological changes in the spleen and thymus of mice. These effects subsequently enhance the serum levels of interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, and immunoglobulin (Ig) A, IgM, and IgG. Furthermore, MRP could also improve CTX-induced oxidative stress, and activate the NF-κB and MAPK pathways in the spleen tissues. The findings reported herein indicate that MRP has a good immunomodulatory activation toward immunosuppressed mice, hence can potentially be developed as an immune adjuvant or functional food.

Identification of bioactive peptides from a Brazilian kefir sample, and their anti-Alzheimer potential in Drosophila melanogaster

Alzheimer’s disease (AD) is the most common form of dementia in the elderly, affecting cognitive, intellectual, and motor functions. Different hypotheses explain AD’s mechanism, such as the amyloidogenic hypothesis. Moreover, this disease is multifactorial, and several studies have shown that gut dysbiosis and oxidative stress influence its pathogenesis. Knowing that kefir is a probiotic used in therapies to restore dysbiosis and that the bioactive peptides present in it have antioxidant properties, we explored its biotechnological potential as a source of molecules capable of modulating the amyloidogenic pathway and reducing oxidative stress, contributing to the treatment of AD. For that, we used Drosophila melanogaster model for AD (AD-like flies). Identification of bioactive peptides in the kefir sample was made by proteomic and peptidomic analyses, followed by in vitro evaluation of antioxidant and acetylcholinesterase inhibition potential. Flies were treated and their motor performance, brain morphology, and oxidative stress evaluated. Finally, we performed molecular docking between the peptides found and the main pathology-related proteins in the flies. The results showed that the fraction with the higher peptide concentration was positive for the parameters evaluated. In conclusion, these results revealed these kefir peptide-rich fractions have therapeutic potential for AD.

Identification of Di/Tripeptide(s) With Osteoblasts Proliferation Stimulation Abilities of Yak Bone Collagen by in silico Screening and Molecular Docking

Endothelial protein C receptor (EPCR), cannabinoid receptor 2 (CBR2), and estrogen receptor α (ERα) play vital roles in osteoblasts proliferation. Also, collagen peptides have osteoblasts proliferation stimulation abilities, and di/tri-peptides could be absorbed by the intestine more easily. This study obtained three di/tripeptides with potential osteoblasts proliferation stimulation abilities of yak bone collagen, namely, MGF, CF, and MF, by in silico screening. Results suggested that these three peptides exhibited good absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties. They also had strong affinities with EPCR, CBR2, and ERα, and the total -CDOCKER energy (-CE) values were 150.9469, 113.1835, and 115.3714 kcal/mol, respectively. However, further Cell Counting Kit-8 (CCK-8) assays indicated that only MGF could significantly (P < 0.05) stimulate osteoblasts proliferation at 0.3 mg/ml. At the same time, the proliferating index (PI) of the osteoblasts treated with MGF increased significantly (P < 0.05), and the alkaline phosphatase (ALP) activity decreased highly significantly (P < 0.01). In summary, MGF exhibited the potential to be an effective treatment for osteoporosis.

Antihypertensive effect and underlying mechanism of tripeptide NCW on spontaneously hypertensive rats using metabolomics analysis

Tripeptide NCW identified in our previous study displayed a strong ACE inhibitory activity, but whether it has any antihypertensive effect in vivo remains unknown. Thus, in this study, we aimed to investigate the protective effects of tripeptide NCW in spontaneously hypertensive rats (SHRs) and to further figure out the serum metabolic profiling variations due to its oral administration via UPLC-Q-TOF-MS/MS-based metabolomics analysis to clarify the underlying hypotensive mechanism. After three weeks of oral administration, the tripeptide NCW-treated group (NCW/SHR group, 80 mg per kg BW per d) showed significantly reduced systolic and diastolic blood pressure by 48.08 ± 3.84 mmHg and 48.92 ± 5.77 mmHg, respectively. Additionally, a total of 25 blood pressure-related metabolites were identified as being significantly changed in SHRs given tripeptide NCW after three weeks. These 25 metabolites might be biomarkers that indicated that the tripeptide NCW exhibits antihypertensive activity via regulating bile acid metabolism, lipid metabolism, amino acid metabolism, purinergic signaling, pantothenate and CoA biosynthesis, and the citrate cycle. Collectively, tripeptide NCW has a protective effect on SHRs associated with serum metabolite abnormalities.

Probing the antioxidant activity of functional proteins and bioactive peptides in Hermetia illucens larvae fed with food wastes

Food waste is becoming more prevalent, and managing it is one of the most important issues in terms of food safety. In this study, functional proteins and bioactive peptides produced from the enzymatic digestion of black soldier fly (Hermetia illucens L., BSF) fed with food wastes were characterized and quantified using proteomics-based analysis. The results revealed approximately 78 peptides and 57 proteins, including 40S ribosomal protein S4, 60S ribosomal protein L8, ATP synthase subunit alpha, ribosomal protein S3, Histone H2A, NADP-glutamate dehydrogenase, Fumarate hydratase, RNA helicase, Chitin binding Peritrophin-A, Lectin C-type protein, etc. were found in BSF. Furthermore, functional analysis of the proteins revealed that the 60S ribosomal protein L5 (RpL5) in BSF interacted with a variety of ribosomal proteins and played a key role in the glycolytic process (AT14039p). Higher antioxidant activity was found in peptide sequences such as GYGFGGGAGCLSMDTGAHLNR, VVPSANRAMVGIVAGGGRIDKPILK, AGLQFPVGR, GFKDQIQDVFK, and GFKDQIQDVFK. It was concluded that the bioconversion of food wastes by BSF brought about the generation of a variety of functional proteins and bioactive peptides with strong antioxidant activity. However, more studies are required to exploit BSF's potential in the value addition of food wastes.

The Potential Effect of Insulin on AChE and Its Interactions with Rivastigmine In Vitro

There is no definite cure for Alzheimer’s disease (AD) due to its multifactorial origin. Drugs that inhibit acetylcholinesterase (AChE), such as rivastigmine, are promising symptomatic treatments for AD. Emerging evidence suggests that insulin therapy can hinder several aspects of AD pathology. Insulin has been shown to modify the activity of AChE, but it is still unknown how insulin and AChE interact. Combination therapy, which targets several features of the disease based on existing medications, can provide a worthy therapy option for AD management. However, to date, no studies have examined the potential interaction of insulin with AChE and/or rivastigmine in vitro. In the present study, we employed the Response Surface Methodology (RSM) as an in vitro assessment to investigate the effect of insulin on both AChE activity and rivastigmine inhibitory action using a common spectrophotometric assay for cholinesterase activity, Ellman’s method. Our results showed that insulin, even at high concentrations, has an insignificant effect on both the activity of AChE and rivastigmine’s inhibitory action. The variance of our data is near zero, which means that the dispersion is negligible. However, to improve our understanding of the possible interaction of insulin and rivastigmine, or its target AChE, more in silico modelling and in vivo studies are needed.

NMCP-2 polysaccharide purified from Morchella conica effectively prevents doxorubicin-induced cardiotoxicity by decreasing cardiomyocyte apoptosis and myocardial oxidative stress

Doxorubicin (DOX) is an anthracycline antibiotic used in the clinical treatment of cancer, but its use is limited due to its cardiotoxic effects. Therefore, it is necessary to explore natural compounds that are effective in protecting against the cardiotoxicity caused by DOX. Neutral Morchella conica polysaccharides-2 (NMCP-2) is a natural polysaccharide with antioxidant activity that was isolated and purified from Morchella conica in our laboratory's previous study. This study aimed to investigate the possible protective effect of NMCP-2 on DOX-induced cardiotoxicity and the potential underlying mechanisms. The model of DOX-induced H9C2 cells and the model of DOX-induced mice were used in this study. In in vitro studies of H9C2 myocardial cells, NMCP-2 effectively increased the activity of H9C2 cells, reducing the levels of lactate dehydrogenase (LDH). In the mouse model of DOX-induced chronic cardiotoxicity, NMCP-2 significantly reduced the cardiac index, reduced the release of serum cardiac enzymes, and improved the pathology of murine myocardial tissues, thereby alleviating DOX-induced cardiotoxicity. Further mechanism studies showed that pretreatment with NMCP-2 counteracted the oxidative stress induced by DOX, as indicated by increasing superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) activities, and malondialdehyde (MDA) production decreased. In addition, we observed NMCP-2 inhibited the activation of the mitochondrial apoptosis pathway and regulated the disordered expression of Bcl-2 and Bax in the myocardial tissues of DOX-treated mice. These findings indicated that NMCP-2, a natural bioactive compound, could potentially be used as a food supplement to reduce the cardiotoxicity caused by DOX.

Potential mechanisms of the anti-hypertensive effects of RVPSL on spontaneously hypertensive rats using non-targeted serum metabolomics

The study aimed to investigate potential mechanisms for the anti-hypertensive effects of RVPSL on spontaneously hypertensive rats (SHRs) using a non-targeted metabonomic approach. In this study, UPLC/MS-based non-targeted metabolomics was performed to discover metabolite variation of serum in SHRs with RVPSL treatment. As a result, the serum metabolites of SHRs that were administered RVPSL for four weeks exhibited distinct alterations. Nine potential biomarkers, i.e., choline, adenosine, adrenic acid, L-tryptophan, niacinamide, glycocholic acid, propiolic acid, D-glyceraldehyde 3-phosphate, and phosphoglycolic acid, were significantly altered, which were mainly involved in lipid metabolism, vitamin and amino acid metabolism, purine metabolism, the MAPK signaling pathway, and the renin-angiotensin system. This study suggested that RVPSL potentially exerted potent effects of alleviating hypertension in the SHRs mainly via integrated regulations of metabolism and production of choline, L-tryptophan, nicotinamide, and adenosine.

Investigation on the characteristics and mechanisms of ACE inhibitory peptides by a thorough analysis of all 8000 tripeptides via binding free energy calculation

Food-derived angiotensin I-converting enzyme (ACE) inhibitory peptides represent a potential source of new antihypertensive. However, their characteristics and binding mechanisms were not well understood. In this study, novel energy calculation and experimentation were combined to elucidate the characteristics and mechanisms of ACE inhibitory tripeptides. ACE inhibitory activity of all 8,000 tripeptides was investigated by in silico experiments. IC50 values of the five top-rated tripeptides ranged from 5.86 to 21.84 μM. Five hundred top-ranked tripeptides were chosen for detailed structure-activity analysis, and a significant preference for aromatic amino acids at both C- and N-terminus was found. By binding free energy analysis of nine representative tripeptides via MM/GBSA, electrostatic energy was found to be the leading energy that contributed to the binding of ACE with its high affinity tripeptides. Besides, S355, V380, and V518, three residues positioned around the classical binding pockets of ACE, also played a key role in ACE's binding. Therefore, for tripeptides, their binding pockets in ACE were redefined. In conclusion, the characteristics of ACE inhibitory peptides were more deeply illustrated by the thorough analysis of all tripeptides. The energy analysis allows a better understanding of the binding mechanisms of ACE inhibitory peptides, which could be used to redesign the ACE inhibitors for stronger inhibitory activity.

Xanthine oxidase inhibitory peptides derived from tuna protein: virtual screening, inhibitory activity, and molecular mechanisms

BACKGROUND

There has been growing interest in the use of xanthine oxidase (XO) as a therapeutic agent to prevent gout and hyperuricemia. In the present study, XO inhibitory peptides were identified from tuna protein by virtual screening, and molecular docking was used to elicit the interaction mechanism between XO and peptides.

RESULTS

A novel tetrapeptide, EEAK, exhibited high XO inhibitory activity with an IC₅₀ of 173.00 ± 0.06 μM. Molecular docking analysis revealed that EEAK bound with the pivotal residues of XO's active sites (i.e., Glu802, Arg880, Glu1261) through two conventional hydrogen bond interactions, two attractive charge interactions, and one salt bridge. EEAK could also bind with the residues Phe649, Leu648, Lys771, Ser876, Phe914, and Thr1010 of XO.

CONCLUSION

This study suggested that conventional hydrogen bond interactions and electrostatic interactions play an important role in XO inhibition. The novel XO inhibitory peptide EEAK from tuna protein could be used as potential candidate for controlling gout and hyperuricemia. © 2020 Society of Chemical Industry.

Characterization and Exploration of Potential Neuroprotective Peptides in Walnut (Juglans regia) Protein Hydrolysate against Cholinergic System Damage and Oxidative Stress in Scopolamine-Induced Cognitive and Memory Impairment Mice and Zebrafish

The purpose of this study was to determine the neuroprotective effect and mechanism of walnut protein hydrolysates (WPH) against memory deficits induced by scopolamine in mice and further to validate the potent neuroprotective peptides identified by integrated approaches of in silico analysis and peptidomics in scopolamine-induced zebrafish. Results showed that a remarkable amelioration on behavioral performance was observed for oral administration of WPH, and disorders of cholinergic system and oxidative stress were normalized in the brains of mice also. Unfortunately, no obvious inflammatory response and anti-inflammatory effect were observed. Additionally, WPH significantly upregulated the expressions of antioxidant defense-related protein (Nrf2) and neurotrophic-related protein (BDNF and CREB). Furthermore, 20 peptides with relatively higher abundance and PeptideRanker scores were predicted by docking to AchE and Keap1. Among them, FY and SGFDAE with the highest binding affinities, -9.8 and -8.0 kcal/mol, were considered as the promising AchE and Keap1 inhibitors, respectively. They were further validated to have neuroprotective capacity in scopolamine-induced zebrafish, indicating that peptidomics and in silico prediction might be the effective approaches to screen neuroprotective peptides.

Preparation and identification of antioxidant peptides from cottonseed proteins

The objective of this study was to investigate the antioxidant properties of cottonseed peptides. Results indicated that cottonseed peptides prepared by enzymatic hydrolysis and microbial fermentation both showed antioxidant properties. The cottonseed protein enzymatic hydrolysate with molecular weight less than 3 kDa exhibited excellent DPPH, ABTS and hydroxyl radical scavenging activity and ferrous ion chelating activity with EC₅₀ values of 0.49 ± 0.02, 2.05 ± 0.02, 2.21 ± 0.12, and 0.99 ± 0.03 mg/mL, respectively. Amino acid composition analysis revealed that cottonseed protein hydrolysates are rich in acidic/basic and aromatic amino acids. In addition, among the 19 identified cottonseed protein-derived peptides, YSNQNGRF had the lowest CDOCKER energy and formed hydrogen bonds with Tyr334, Arg380, Arg415, Ser508, and Ser602, and van der Waals interactions with Asn382, Tyr525, Gln530, and Ser555, which all located in the binding site of Keap1-Nrf2 interaction. These findings suggested that the antioxidant peptides from cottonseed protein had the potential as functional ingredients in foods.

Identification of novel umami peptides from myosin via homology modeling and molecular docking

The structure of the umami receptor T1R1/T1R3 was constructed using homology modeling and molecular dynamics, and the interactions between peptides and this umami receptor were studied by molecular docking. The umami intensity of the peptides was also investigated by using an electronic tongue. The results showed that 99.3% of the amino acid residues in the homologous model of the T1R1/T1R3 heterodimer were within the allowable range, which is greater than the threshold requirement of 90% of the residues in the high-quality model structure. Five novel peptides (DK, EEK, EDQK, SEGGR, and QDSIGS) were selected and synthesized. The umami intensity of these five peptides was stronger than that of monosodium glutamate. The docking results revealed that the interactions between peptides and the major amino acids residues Arg151, Asp147, and Gln52 of T1R1 play critical roles in the production of umami taste.

AGLPM and QMDDQ peptides exert a synergistic action on memory improvement against scopolamine-induced amnesiac mice

This study aimed to explore the synergistic action of pentapeptides Gln-Met-Asp-Asp-Gln (QMDDQ) and Ala-Gly-Leu-Pro-Met (AGLPM) on memory improvement against scopolamine-induced impairment in mice compared to those of either peptide alone. In behavioral tests, the codelivery of QMDDQ and AGLPM was superior to the individual supplements of either peptide alone not only in enhancing the memory ability at training trials but also in recovering the memory impairment in scopolamine-induced amnesiac mice in test trials. Furthermore, combination treatment with QMDDQ and AGLPM could significantly reduce the acetylcholinesterase (AChE) level and increase the acetylcholine (ACh) level in the hippocampus, and noticeably improve the pathological morphology of the neuron cells in hippocampal regions CA1 and CA2 and dentate gyrus (DG). The findings indicated that the combination treatment with QMDDQ and AGLPM could improve the memory function by regulating the cholinergic system.

Identification of tuna protein-derived peptides as potent SARS-CoV-2 inhibitors via molecular docking and molecular dynamic simulation

The present study aimed to identify potential SARS-CoV-2 inhibitory peptides from tuna protein by virtual screening. The molecular docking was performed to elicit the interaction mechanism between targets (M^pro and ACE2) and peptides. As a result, a potential antiviral peptide EEAGGATAAQIEM (E-M) was identified. Molecular docking analysis revealed that E-M could interact with residues Thr190, Thr25, Thr26, Ala191, Leu50, Met165, Gln189, Glu166, His164, His41, Cys145, Gly143, and Asn119 of M^pro via 11 conventional hydrogen bonds, 9 carbon hydrogen bonds, and one alkyl interaction. The formation of hydrogen bonds between peptide E-M and the residues Gly143 and Gln189 of M^pro may play important roles in inhibiting the activity of M^pro. Besides, E-M could bind with the residues His34, Phe28, Thr27, Ala36, Asp355, Glu37, Gln24, Ser19, Tyr83, and Tyr41 of ACE2. Hydrogen bonds and electrostatic interactions may play vital roles in blocking the receptor ACE2 binding with SARS-CoV-2.