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In this study, flavourzyme, papain, neutrase, and alcalase, as well as gastrointestinal digestion simulated with pepsin and pancreatin, were used to hydrolyze oat protein, and the dipeptidyl peptidase-IV (DPP-IV) inhibitory activities of the oat protein hydrolysates were investigated. The results indicated that the oat protein hydrolysate by neutrase showed the most potent DPP-IV inhibitory property with an IC50 value of 2.55 ± 0.38 mg/mL. Using UPLC-MS/MS, ten new DPP-IV inhibitory peptides were identified from the oat protein hydrolysate by neutrase. Among these peptides, IPQHY, VPQHY, VAVVPF, and VPLGGF exhibited the strongest DPP-IV inhibitory activity with IC50 values below 50 μM, and all of them acted as mixed-type inhibitors. Molecular docking indicated that the above four oat-derived peptides were predicted to form hydrogen bonds, attractive charge, and hydrophobic interactions with the residues of the active site of DPP-IV. Therefore, our results suggest that oat is an excellent protein source for food-derived DPP-IV inhibitory peptides and it has the prospect of becoming a dietary supplement for T2DM. [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

Summary: Previous work has demonstrated that peptides QIGLF and RVPSL exhibited in vitro ACE inhibitory activity. This study was aimed to evaluate the in vivo anti‐hypertensive effects of peptides RVPSL and QIGLF using animal experiments, and clarify the molecular mechanisms of interaction between ACE and peptides by molecular docking. In this work, the systolic blood pressure (SBP) of SHRs treated with QIGLF and RVPSL decreased by 48 ± 6 and 46 ± 6 mmHg, respectively. Docking results revealed that QIGLF and RVPSL established interactions with three main actives that of ACE, that is, S1 (Ala 354), S2 (Gln 281, His 513, Tyr 520 and Lys 511) and S1' (Glu 162). These interactions can prevent ACE from binding to substrate and competitive inhibition. The in vivo anti‐hypertensive effect of QIGLF and RVPSL was consistent with their in vitro ACE inhibitory activity. QIGLF and RVPSL have potential to be a healthy functional food with anti‐hypertensive effects. [ABSTRACT FROM AUTHOR]

BACKGROUND Alzheimer's disease (AD) is a kind of progressive neurodegenerative disease that affects the elderly. There is no ideal treatment for AD. Thus, the purpose of this study is to identify anti‐AD peptides from ovalbumin. RESULTS: The potential tripeptides IEK, LYR, and CIK were selected for molecular docking. The '‐CDOCKER_Energy' values of the best docking positions of the tripeptide IEK, LYR, and CIK interacting with acetylcholinesterase (AChE) were 93.8119, 86.9556 and 73.6370 kcal mol−1, respectively. The '‐CDOCKER_Energy' values for interaction with butyrylcholinesterase (BChE) were 96.6386, 80.8392, and 87.4341 kcal mol−1, respectively. Most importantly, the '‐CDOCKER_Energy' values for interaction with β‐site amyloid precursor protein cleavage enzyme1 (BACE1) were 85.5903, 71.3342, and 68.4290 kcal mol−1, respectively. Overall, in vitro assay results demonstrated that the peptide CIK exhibited impressive inhibitory activities against AChE, BChE, and BACE1, with half maximal inhibitory concentration (IC50) values of 6.76, 7.72, and 34.48 μmol L−1, respectively. In particular, CIK can be joined with some peripheral anion sites (PAS) and catalytic sites on AChE, BChE, and BACE1. CONCLUSION: Tripeptide CIK can effectively inhibit the activities of AChE, BChE, and BACE1. Tripeptide CIK therefore has the potential to treat AD effectively. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: Excessive concentrations of angiotensin‐converting enzyme (ACE) can give rise to high blood pressure, and is harmful to the body. ACE inhibitory peptides from food proteins are considered good sources of function food. However, the preparation of ACE inhibitory peptides by classical method faces many challenges. Three novel ACE inhibitory peptides were identified by in silico methods, and showed potent activity against ACE in vitro. The simulation hydrolysis of nebulin was performed with ExPASy PeptideCutter program. Potential activity, solubility, and absorption, distribution, metabolism, excretion, and toxicity properties of generated peptides were predicted using program online. Molecular docking displayed that EGF, HGR, and VDF were docked into the S1 and S2 pockets of ACE. Meanwhile, Phe and Arg at the C‐terminal enhance ACE affinity. The IC50 values of EGF, HGR, and VDF were 474.65 ± 0.08, 106.21 ± 0.52, and 439.27 ± 0.09 μM, respectively. Three peptides EGF, HGR, and VDF from Oncorhynchus mykiss nebulin were identified, and the molecular mechanism between ACE and peptides was clarified using in silico methods. The results suggested that Oncorhynchus mykiss nebulin would be an attractive raw material of antihypertensive nutraceutical ingredients. Practical Application: This study has shown the potential of Oncorhynchus mykiss nebulin as good sources for producing ACE inhibitory peptides. According to this finding, in silico approach is the feasible way for prediction and identification of food‐derived ACE inhibitory peptides in emerging nutraceutical field. [ABSTRACT FROM AUTHOR]

Aminopeptidase N (APN) is an important zinc-dependent metalloproteinase expressed on cell surfaces. This study was done to find APN inhibitory peptides using virtual screening and molecular docking. Hen egg proteins were cleaved using pepsin and trypsin in silico to peptides of different lengths. Dipeptides and tripeptides are more easily absorbed in the gastrointestinal tract (GIT). The bioactivity, solubility, absorption, distribution, metabolism, excretion, and toxicity properties of the dipeptides and tripeptides were then predicted. APN was used as a molecular docking target for potential peptides. The tripeptides CNR, CDR and GEF were docked with the APN residues, His388, His392, Glu411, Glu355 and Tyr477. An in vitro APN inhibition assay showed that the IC 50 values of CNR, CDR and GEF against APN were 8.94, 6.42, and 61.7 mM, respectively. • Three APN inhibitory peptides CNR, CDR, and GEF were identified. • APN inhibition IC 50 values of CNR, CDR, and GEF were 8.94, 6.42 and 61.7 mM, respectively. • CNR, CDR, and GEF blocked APN using active sites and zinc-binding groups. [ABSTRACT FROM AUTHOR]

• Three new ACE and DPP-IV inhibitory peptides were identified from egg. • IC 50 values of ADF, MIR, and FGR against ACE were 27.75 mM, 24.97 mM and 66.98 μM. • IC 50 values of ADF, MIR and FGR against DPP-IV were 16.83, 4.86 and 46.22 mM. Angiotensin converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV) are important membrane peptidases. The inhibition of ACE and DPP-IV enzymes has become a key therapeutic target for the treatment of hypertension and diabetes. This study was conducted to discover membrane peptidase inhibitory peptides that inhibit ACE and DPP-IV. Egg proteins were cleaved by pepsin and trypsin in silico. The potential activity, solubility, absorption, distribution, metabolism, excretion, and toxicity of the peptides were then predicted online. Finally, ACE and DPP-IV were applied as molecular docking targets for the potential peptides. After simulating gastrointestinal digestion, the IC 50 values of ADF, MIR, and FGR against ACE activity were 27.75 ± 0.90 mM, 24.97 ± 0.80 mM, and 66.98 ± 1.40 μM, against DPP-IV activity were 16.83 mM, 4.86 mM, and 46.22 mM, respectively. The ACE and DPP-IV inhibitory peptides identified from hen egg proteins can be used as functional food ingredients for controlling hypertension and diabetes. [ABSTRACT FROM AUTHOR]

The widespread application of soybean‐derived peptides is currently limited due to the challenges in the identification of peptides. In the present work, in silico and in vitro analysis were applied to identify ACE inhibitory tri‐peptides from soybean protein. The soybean protein was cleaved by PeptideCutter. Then, unknown tri‐peptides were selected to solubility estimation and ADME prediction. Subsequently, Discovery Studio was applied to evaluate the interaction mechanism between ACE and tri‐peptides. Finally, in vitro activity of theoretical ACE inhibitory tri‐peptides was verified by RP‐HPLC method. As a result, DMG was selected as a potent ACE inhibitory peptide. Cell experiment showed that DMG had no cytotoxic effects on HEK‐293 cells. And molecular docking results indicated that DMG contacted well with ACE's active sites (Gln281, His353, Ala354, Glu384, Lys511, His513, and Tyr520). Furthermore, DMG could exert potent activity against ACE, with IC50 value of 3.95 ± 0.11 mM. Practical applications: Present research showed soybean is a potential protein resource to obtain ACE inhibitory peptides. Simultaneously, virtual screening method is a feasible way to substitute for classical method in emerging nutritional fields. What's more, present study provides a theoretical basis for industrial research on foodstuff for ACE inhibitory peptides without side effects. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quinoa protein hydrolysates < 1 kDa inhibited in-vitro and in-situ DPP-IV activities. • Quinoa germinated for 2 h significantly increased the DPP-IV inhibitory activities. • Quinoa peptides IPI and IPV showed DPP-IV inhibitory activities with IC 50 < 30 μM in-vitro and in-situ. • IPI and IPV behaved as competitive inhibitors on DPP-IV. • IPI and IPV bound to DPP-IV with hydrogen bonds, attractive charge, and hydrophobic interactions. The objective of this study was to investigate the dipeptidyl peptidase IV (DPP-IV) inhibitory properties of quinoa protein-derived peptides. After germination, quinoa protein was extracted and then hydrolyzed by different enzymes such as papain, Alcalase, Neutrase, and Flavourzyme and pepsin-trypsin digestion. Results showed that the quinoa protein hydrolysates (QPH) by pepsin-trypsin digestion displayed the highest DPP-IV inhibitory activity. When ultrafiltrated, the fraction of quinoa protein hydrolysate with molecular weight less than 1 kDa (QPH1) exhibited a superior DPP-IV inhibitory activity with IC 50 of 3.40 ± 0.20 mg/mL in vitro and 2.20 ± 0.29 mg/mL in Caco-2 based in situ. Furthermore, the peptide sequences of QPH1 were identified by UPLC-MS/MS. Twenty quinoa-derived peptides were determined with in vitro DPP-IV inhibitory activities with IC 50 values less than 500 μM. The peptides IPI, IPV, VAYPL and IPIN showed the highest in vitro DPP-IV inhibitory activities with IC 50 of 5.25 ± 0.16, 26.15 ± 0.58, 42.93 ± 1.15, and 56.58 ± 3.36 μM, respectively. The in situ DPP-IV activities of Caco-2 cells were also attenuated by these four peptides with IC 50 of 10.75 ± 0.87, 29.11 ± 1.79, 61.9 ± 4.23, and 92.59 ± 12.89 µM, respectively. Moreover, these four peptides were identified as competitive inhibitors of DPP-IV. Molecular docking showed that quinoa peptides IPI and IPV were predicted to form multiple hydrogen bonds, attractive charge, and hydrophobic interactions with the residues of active site of DPP-IV. This study confirms that quinoa protein is a good source for DPP-IV inhibitory peptides and has potential as ingredients in functional foods for the prevention or management of type 2 diabetes. [ABSTRACT FROM AUTHOR]

COVID-19 is a global health emergency that causes serious concerns. A global effort is underway to identify drugs for the treatment of COVID-19. One possible solution to the present problem is to develop drugs that can inhibit SARS-CoV-2 main protease (Mpro), a coronavirus protein that been considered as one among many drug targets. In this work, lactoferrin from Bos taurus L. was in silico hydrolyzed. The bioactivity, water solubility, and ADMET properties of the generated peptides were predicted using various online tools. The molecular interactions between Mpro and the peptides were studied using molecular docking and molecular dynamic simulation. The results demonstrated that peptide GSRY was predicted to have better physicochemical properties, and the value of '-C DOCKER interaction energy' between peptide GSRY and Mpro was 80.8505 kcal/mol. The interaction between the peptide GSRY and the native ligand N3 co-crystallized with Mpro had overlapped amino acids, i.e., HIS163, GlY143, GLU166, GLN189 and MET165. Molecular dynamic simulation revealed that Mpro/GSRY complexes were stable. Collectively, the peptide GSRY may be a potential candidate drug against Mpro of SARS-CoV-2. • The bioactivity value of GSRY was 0.54, and its adsorption rate is 21.72%. • GSRY possessed the binding potential towards to Mpro of SARS-CoV-2 virus. • The interaction of the peptide GSRY and inhibitor N3 with the Mpro have overlapping amino acids. [ABSTRACT FROM AUTHOR]

• Five novel umami peptieds DK, EEK, EDQK, SEGGR, and QDSIGS were identified. • Interaction mechanism of umami peptides and T1R1/T1R3 was investigated by CDOCKER. • Arg151, Asp147 and Gln52 in T1R1 play critical roles in the production of umami taste. 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. [ABSTRACT FROM AUTHOR]