Molecular Mechanism for the α-Glucosidase Inhibitory Effect of Wheat Germ Peptides

Extraction, identification, and molecular mechanisms of α-glucosidase inhibitory peptides from defatted Antarctic krill (Euphausia superba) powder hydrolysates

The objective of this study was to explore the potential of Antarctic krill-derived peptides as α-glucosidase inhibitors for the treatment of type 2 diabetes. The enzymolysis conditions of α-glucosidase inhibitory peptides were optimized by response surface methodology (RSM), a statistical method that efficiently determines optimal conditions with a limited number of experiments. Gel chromatography and LC-MS/MS techniques were utilized to determine the molecular weight (Mw) distribution and sequences of the hydrolysates. The identification and analysis of the mechanism behind α-glucosidase inhibitory peptides were conducted through conventional and computer-assisted techniques. The binding affinities between peptides and α-glucosidase were further validated using BLI (biolayer interferometry) assay. The results revealed that hydrolysates generated by neutrase exhibited the highest α-glucosidase inhibition rate. Optimal conditions for hydrolysis were determined to be an enzyme concentration of 6 × 103 U/g, hydrolysis time of 5.4 h, and hydrolysis temperature of 45 °C. Four peptides (LPFQR, PSFD, PSFDF, VPFPR) with strong binding affinities to the active site of α-glucosidase, primarily through hydrogen bonding and hydrophobic interactions. This study highlights the prospective utility of Antarctic krill-derived peptides in curtailing α-glucosidase activity, offering a theoretical foundation for the development of novel α-glucosidase inhibitors and related functional foods to enhance diabetes management.

Rapid screening of the novel bioactive peptides with notable α-glucosidase inhibitory activity by UF-LC-MS/MS combined with three-AI-tool from black beans

This work aimed to propose a rapid method to screen the bioactive peptides with anti-α-glucosidase activity instead of traditional multiple laborious purification and identification procedures. 242 peptides binding to α-glycosidase were quickly screened and identified by bio-affinity ultrafiltration combined with LC-MS/MS from the double enzymatic hydrolysate of black beans. Top three peptides with notable anti-α-glucosidase activity, NNNPFKF, RADLPGVK and FLKEAFGV were further rapidly screened and ranked by the three artificial intelligence tools (three-AI-tool) BIOPEP database, PeptideRanker and molecular docking from the 242 peptides. Their IC50 values were in order as 4.20 ± 0.11 mg/mL, 2.83 ± 0.03 mg/mL, 1.32 ± 0.09 mg/mL, which was opposite to AI ranking, for the hydrophobicity index of the peptides was not included in the screening criteria. According to the kinetics, FT-IR, CD and ITC analyses, the binding of the three peptides to α-glucosidase is a spontaneous and irreversible endothermic reaction that results from hydrogen bonds and hydrophobic interactions, which mainly changes the α-helix structure of α-glucosidase. The peptide-activity can be evaluated vividly by AFM in vitro. In vivo, the screened FLKEAFGV and RADLPGVK can lower blood sugar levels as effectively as acarbose, they are expected to be an alternative to synthetic drugs for the treatment of Type 2 diabetes.

Screening of α-Glucosidase Inhibitors in Cichorium glandulosum Boiss. et Huet Extracts and Study of Interaction Mechanisms

Cichorium glandulosum Boiss. et Huet (CGB) extract has an α-glucosidase inhibitory effect (IC50 = 59.34 ± 0.07 μg/mL, positive control drug acarbose IC50 = 126.1 ± 0.02 μg/mL), but the precise enzyme inhibitors implicated in this process are not known. The screening of α-glucosidase inhibitors in CGB extracts was conducted by bioaffinity ultrafiltration, and six potential inhibitors (quercetin, lactucin, 3-O-methylquercetin, hyperoside, lactucopicrin, and isochlorogenic acid B) were screened as the precise inhibitors. The binding rate calculations and evaluation of enzyme inhibitory effects showed that lactucin and lactucopicrin exhibited the greatest inhibitory activities. Next, the inhibiting effects of the active components of CGB, lactucin and lactucopicrin, on α-glucosidase and their mechanisms were investigated through α-glucosidase activity assay, enzyme kinetics, multispectral analysis, and molecular docking simulation. The findings demonstrated that lactucin (IC50 = 52.76 ± 0.21 μM) and lactucopicrin (IC50 = 17.71 ± 0.64 μM) exhibited more inhibitory effects on α-glucosidase in comparison to acarbose (positive drug, IC50 = 195.2 ± 0.30 μM). Enzyme kinetic research revealed that lactucin inhibits α-glucosidase through a noncompetitive inhibition mechanism, while lactucopicrin inhibits it through a competitive inhibition mechanism. The fluorescence results suggested that lactucin and lactucopicrin effectively reduce the fluorescence of α-glucosidase by creating lactucin-α-glucosidase and lactucopicrin-α-glucosidase complexes through static quenching. Furthermore, the circular dichroism (CD) and Fourier transform infrared spectroscopy (FT-IR) analyses revealed that the interaction between lactucin or lactucopicrin and α-glucosidase resulted in a modification of the α-glucosidase's conformation. The findings from molecular docking and molecular dynamics simulations offer further confirmation that lactucopicrin has a robust binding affinity for certain residues located within the active cavity of α-glucosidase. Furthermore, it has a greater affinity for α-glucosidase compared to lactucin. The results validate the suppressive impact of lactucin and lactucopicrin on α-glucosidase and elucidate their underlying processes. Additionally, they serve as a foundation for the structural alteration of sesquiterpene derived from CGB, with the intention of using it for the management of diabetic mellitus.

Identification of Novel Peptides in Distillers' Grains as Antioxidants, α-Glucosidase Inhibitors, and Insulin Sensitizers: In Silico and In Vitro Evaluation

Distillers' grains are rich in protein and constitute a high-quality source of various bioactive peptides. The purpose of this study is to identify novel bioactive peptides with α-glucosidase inhibitory, antioxidant, and insulin resistance-ameliorating effects from distiller's grains protein hydrolysate. Three novel peptides (YPLPR, AFEPLR, and NDPF) showed good potential bioactivities, and the YPLPR peptide had the strongest bioactivities, whose IC50 values towards α-glucosidase inhibition, radical scavenging rates of 2,2'-azino-bis (3-ethylbenzothiazoline-6- sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) were about 5.31 mmol/L, 6.05 mmol/L, and 7.94 mmol/L, respectively. The glucose consumption of HepG2 cells treated with YPLPR increased significantly under insulin resistance condition. Moreover, the YPLPR peptide also had a good scavenging effect on intracellular reactive oxygen species (ROS) induced by H2O2 (the relative contents: 102.35% vs. 100%). Molecular docking results showed that these peptides could stably combine with α-glucosidase, ABTS, and DPPH free radicals, as well as related targets of the insulin signaling pathway through hydrogen bonding and van der Waals forces. This research presents a potentially valuable natural resource for reducing oxidative stress damage and regulating blood glucose in diabetes, thereby increasing the usage of distillers' grains peptides and boosting their economic worth.

Integration of cloud-based molecular networking and docking for enhanced umami peptide screening from Pixian douban

This study presents an innovative cloud-based approach, using Pixian Douban, a well-known Chinese fermented seasoning, as a case study, to improve the identification of umami peptides and explore their interactions with the T1R1/T1R3 receptor. A feature-based molecular networking method was utilized to rapidly identify a total of eighteen peptides, including seven previously unrecorded ones. Notably, the umami threshold of QIVK in an aqueous solution was determined to be 0.3215 mmol/L, surpassing the majority of peptides reported in the past three years. Molecular docking analysis further revealed the strong binding of QIVK to T1R3 receptor residues through hydrogen bonds, as well as interactions via salt bridges and electrostatic attractions. As a result, this research significantly contributes to the efficient screening of umami peptides and the elucidation of the molecular basis of umami sensory perception in complex food systems.

Identification and molecular mechanism of novel bifunctional peptides from Duroc × (Landrace × Yorkshire) pig dry-cured ham: A peptidomics and in silico analysis

Duroc × (Landrace × Yorkshire) pigs are popular in the Chinese market because of their rapid growth, leanness, and economic value. Despite their widespread use in dry-cured ham processing, there is a lack of research on the bioactive peptides of Duroc × (Landrace × Yorkshire) pig ham (DLYH). This study aimed to investigate the presence of peptides with antioxidant and α-glucosidase inhibitory activities in DLYH using peptidomics and in silico analysis. A total of 453 peptides were identified from DLYH, originating mainly from myosin, actin, and the EF-hand domain-containing protein. Notably, two peptides, YDEAGPSIVH (YH10) and FAGDDAPRAVF (FF11), emerged as novel bioactive peptides with antioxidant and α-glucosidase inhibitory activities. Among these peptides, YH10 exhibited a high DPPH radical scavenging activity (IC50 = 1.93 mM), ABTS radical scavenging activity (IC50 = 0.10 mM), α-glucosidase inhibitory activity (IC50 = 2.13 mM), and good gastrointestinal tolerance. Molecular docking analysis showed that YH10 was bound to the ABTS and DPPH radicals and the active site of α-glucosidase (3A4A) primarily through hydrogen bonding and hydrophobic interactions. Furthermore, molecular dynamics (MD) simulation indicated that the YH10-3A4A complexes maintained stable and compact conformations. In conclusion, our findings indicated that peptide YH10 derived from DLYH possesses bifunctional properties of α-glucosidase inhibition and antioxidant activity, which could be beneficial for maintaining ham quality and promoting human health.

Porcupine quills keratin peptides induces G0/G1 cell cycle arrest and apoptosis via p53/p21 pathway and caspase cascade reaction in MCF-7 breast cancer cells

BACKGROUND

Porcupine quills, a by-product of porcupine pork, are rich in keratin, which is an excellent source of bioactive peptides. The objective of this study was to investigate the underlying mechanism of anti-proliferation effect of porcupine quills keratin peptides (PQKPs) on MCF-7 cells.

RESULTS

Results showed that PQKPs induced MCF-7 cells apoptosis by significantly decreasing the secretion level of anti-apoptosis protein Bcl-2 and increasing the secretion levels of pro-apoptosis proteins Bax, cytochrome c, caspase 9, caspase 3 and PARP. PQKPs also arrested the cell cycle at G0/G1 phase via remarkably reducing the protein levels of CDK4 and enhancing the protein levels of p53 and p21. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analysis identified nine peptides with molecular weights less than 1000 Da in PQKPs. Molecular docking results showed that TPGPPT and KGPAC identified from PQKPs could bind with p53 mutant and Bcl-2 protein by conventional hydrogen bonds, carbon hydrogen bonds and van der Waals force. Furthermore, the anti-proliferation impact of synthesized peptides (TPGPPT and KGPAC) was shown in MCF-7 cells.

CONCLUSION

These findings indicated that PQKPs suppressed the proliferation of MCF-7 breast cancer cells by triggering apoptosis and G0/G1 cell cycle arrest. Moreover, the outcome of this study will bring fresh insights into the production and application of animal byproducts. © 2023 Society of Chemical Industry.

An Update on Dipeptidyl Peptidase-IV Inhibiting Peptides

Diabetes is a chronic metabolic disorder. According to the International Diabetes Federation, about 537 million people are living with diabetes. The two types of diabetes are type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM), among which the population affected by T2DM is relatively higher. A major reason for T2DM is that insulin stimulation is hampered due to the inactivation of incretin hormones. Dipeptidyl peptidase-IV (DPP-IV) is a serine protease that is directly involved in the inactivation of incretin hormones, e.g., glucagon-like peptide-1 (GLP-1). Therefore, the inhibition of DPP-IV can be a promising method for managing T2DM, in addition to other enzyme inhibition strategies, such as inhibition of α-amylase and α -glucosidase. Currently, about 12 different gliptin drugs are available in the market that inhibit DPP-IV in a dose-dependent manner. Instead of gliptins, 'peptides' can also be employed as an alternative and promising way to inhibit DPP-IV. Peptide inhibitors of DPP-IV have been identified from various plants and animals. Chemically synthesized peptides have also been experimented for inhibiting DPP-IV. Most peptides have been analysed by biochemical assays, whereas some in vitro assays have also been reported. Molecular docking analysis has been applied to comprehend the mechanism of inhibition. In this review, certain aspects of natural as well as synthetic peptides are described that have been proven to inhibit DPP-IV.

Virtual Screening Technology for Two Novel Peptides in Soybean as Inhibitors of α-Amylase and α-Glucosidase

Soybean peptides (SPs) have bioactivities of enzyme inhibition that are beneficial to human health, but their mechanism is not clear. This study aimed to identify peptide fragments in SPs that simultaneously inhibit α-amylase and α-glucosidase and to explore their enzyme inhibition mechanism. Firstly, the inhibitory activity of SPs against the enzymes was determined. And two octapeptides, LDQTPRVF and SRNPIYSN, were identified for the first time by using HPLC-QTOF-MS/MS and virtual screening. Molecular simulation results showed that hydrogen bonds and π-π bonds were the key factors, and the N-terminal (Leu and Ser) and C-terminal (Phe) of peptide were important inhibiting sites. Both octapeptides were synthesized, and their IC50 values were 3.08 and 5.58 mmol/L for α-amylase, and 2.52 and 4.57 mmol/L for α-glucosidase, respectively. This study provided evidence for SPs as a potential inhibitor of α-amylase and α-glucosidase in special dietary foods.

Emerging therapeutic options in the management of diabetes: recent trends, challenges and future directions

Diabetes is a serious health issue that causes a progressive dysregulation of carbohydrate metabolism due to insufficient insulin hormone, leading to consistently high blood glucose levels. According to the epidemiological data, the prevalence of diabetes has been increasing globally, affecting millions of individuals. It is a long-term condition that increases the risk of various diseases caused by damage to small and large blood vessels. There are two main subtypes of diabetes: type 1 and type 2, with type 2 being the most prevalent. Genetic and molecular studies have identified several genetic variants and metabolic pathways that contribute to the development and progression of diabetes. Current treatments include gene therapy, stem cell therapy, statin therapy, and other drugs. Moreover, recent advancements in therapeutics have also focused on developing novel drugs targeting these pathways, including incretin mimetics, SGLT2 inhibitors, and GLP-1 receptor agonists, which have shown promising results in improving glycemic control and reducing the risk of complications. However, these treatments are often expensive, inaccessible to patients in underdeveloped countries, and can have severe side effects. Peptides, such as glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), are being explored as a potential therapy for diabetes. These peptides are postprandial glucose-dependent pancreatic beta-cell insulin secretagogues and have received much attention as a possible treatment option. Despite these advances, diabetes remains a major health challenge, and further research is needed to develop effective treatments and prevent its complications. This review covers various aspects of diabetes, including epidemiology, genetic and molecular basis, and recent advancements in therapeutics including herbal and synthetic peptides.

The inhibitory mechanism of amylase inhibitors and research progress in nanoparticle-based inhibitors

Type 2 diabetes is caused by persistently high blood sugar levels, which leads to metabolic dysregulation and an increase in the risk of chronic diseases such as diabetes and obesity. High levels of rapidly digestible starches within foods may contribute to high blood sugar levels. Amylase inhibitors can reduce amylase activity, thereby inhibiting starch hydrolysis, and reducing blood sugar levels. Currently, amylase inhibitors are usually chemically synthesized substances, which can have undesirable side effects on the human body. The development of amylase inhibitors from food-grade ingredients that can be incorporated into the human diet is therefore of great interest. Several classes of phytochemicals, including polyphenols and flavonoids, have been shown to inhibit amylase, including certain types of food-grade nanoparticles. In this review, we summarize the main functions and characteristics of amylases within the human body, as well as their interactions with amylase inhibitors. A strong focus is given to the utilization of nanoparticles as amylase inhibitors. The information covered in this article may be useful for the design of functional foods that can better control blood glucose levels, which may help reduce the risk of diabetes and other diet-related diseases.

Screening and Activity Analysis of α-Glucosidase Inhibitory Peptides Derived from Coix Seed Prolamins Using Bioinformatics and Molecular Docking

Hydrolysates of coix seed prolamins (CHPs) have an excellent hypoglycemic effect and can effectively inhibit α-glucosidase, which is the therapeutic target enzyme for type 2 diabetes mellitus. However, its hypoglycemic components and molecular mechanisms remain unclear, and its stability in food processing needs to be explored. In this study, four potential α-glucosidase inhibitory peptides (LFPSNPLA, FPCNPLV, HLPFNPQ, LLPFYPN) were identified and screened from CHPs using LC-MS/MS and virtual screening techniques. The results of molecular docking showed that the four peptides mainly inhibited α-glucosidase activity through hydrogen bonding and hydrophobic interactions, with Pro and Leu in the peptides playing important roles. In addition, CHPs can maintain good activity under high temperatures (40~100 °C) and weakly acidic or weakly alkaline conditions (pH 6.0~8.0). The addition of glucose (at 100 °C) and NaCl increased the inhibitory activity of α-glucosidase in CHPs. The addition of metal ions significantly decreased the inhibitory activity of α-glucosidase by CHPs, and their effects varied in magnitude with Cu2+ having the largest effect followed by Zn2+, Fe3+, K+, Mg2+, and Ca2+. These results further highlight the potential of CHPs as a foodborne hypoglycemic ingredient, providing a theoretical basis for the application of CHPs in the healthy food industry.

Development and Identification of Novel α-Glucosidase Inhibitory Peptides from Mulberry Leaves

The mulberry leaf is a botanical resource that possesses a substantial quantity of protein. In this study, alcalase hydrolysis conditions of mulberry leaf protein were optimized using the response surface method. The results showed that the optimum conditions were as follows: substrate protein concentration was 0.5% (w/v), enzymatic hydrolysis temperature was 53.0 °C, enzymatic hydrolysis time was 4.7 h, enzyme amount was 17,800 U/g, and pH was 10.5. Then mulberry leaf peptides were separated by ultrafiltration according to molecular weight. Peptides (<3 kDa) were screened and subsequently identified using LC-MS/MS after the evaluation of α-glucosidase inhibition across various fractions. Three novel potential bioactive peptides RWPFFAFM (1101.32 Da), AAGRLPGY (803.91 Da), and VVRDFHNA (957.04 Da) with the lowest average docking energy were screened for molecular dynamics simulation to examine their binding stability with enzymes in a 37 °C simulated human environment. Finally, they were prepared by solid phase synthesis for in vitro verification. The former two peptides exhibited better IC50 values (1.299 mM and 1.319 mM, respectively). These results suggest that the α-glucosidase inhibitory peptides from mulberry leaf protein are potential functional foods or drugs for diabetes treatment, but further in vivo studies are needed to identify the bioavailability and toxicity.

Alpha-Glucosidase Inhibitory Peptides: Sources, Preparations, Identifications, and Action Mechanisms

With the change in people's lifestyle, diabetes has emerged as a chronic disease that poses a serious threat to human health, alongside tumor, cardiovascular, and cerebrovascular diseases. α-glucosidase inhibitors, which are oral drugs, have proven effective in preventing and managing this disease. Studies have suggested that bioactive peptides could serve as a potential source of α-glucosidase inhibitors. These peptides possess certain hypoglycemic activity and can effectively regulate postprandial blood glucose levels by inhibiting α-glucosidase activity, thus intervening and regulating diabetes. This paper provides a systematic summary of the sources, isolation, purification, bioavailability, and possible mechanisms of α-glucosidase inhibitory peptides. The sources of the α-glucosidase inhibitory peptides were introduced with emphasis on animals, plants, and microorganisms. This paper also points out the problems in the research process of α-glucosidase inhibitory peptide, with a view to providing certain theoretical support for the further study of this peptide.

Preparation, identification, and inhibitory mechanism of dipeptidyl peptidase IV inhibitory peptides from goat milk whey protein

This study explores potential hypoglycemic mechanisms by preparing and identifying novel dipeptidyl peptidase IV (DPP-IV) inhibitory peptides from goat milk (GM) whey protein. Papain was used to hydrolyze the GM whey protein. After purification by ultrafiltration, the Sephadex column, and preparative RP-HPLC, the peptide inhibited DPP-IV, α-glucosidase, and α-amylase with IC50 of 0.34, 0.37, and 0.72 mg/mL, respectively. To further explore the inhibitory mechanism of peptides on DPP-IV, SPPEFLR, LDADGSY, YPVEPFT, and FNPTY were identified and synthesized for the first time, with IC50 values of 56.22, 52.16, 175.7, and 62.32 µM, respectively. Molecular docking and dynamics results show that SPPEFLR, LDADGSY, and FNPTY bind more tightly to the active pocket of DPP-IV, which was consistent with the in vitro activity. Furthermore, the first three N-terminals of SPPEFLR and FNPTY peptides exhibit proline characteristics and competitively inhibit DPP-IV. Notably, the first N-terminal leucine of LDADGSY may play a key role in inhibiting DPP-IV.

Flexible processing technology of coix seed prolamins by combined heat-ultrasound: Effects on their enzymatic hydrolysis characteristics and the hypoglycemic activities of derived peptides

The self-assembled structures of coix seeds affected the enzymatic efficiency and doesn't facilitate the release of more active peptides. The influence of heating combined with ultrasound pretreatment (HT + US) on the structure, enzymatic properties and hydrolysates (CHPs) of coix seed prolamin was investigated. Results showed that the structural of coix seed prolamins has changed after HT + US, including increased surface hydrophobicity, reduced α-helix and random coil content, and a decrease in particle size. So that, leads to changes in thermodynamic parameters such as an increase in the reaction rate constant and a decrease in activation energy, enthalpy and enthalpy. The fractions of <1000 Da, degree of hydrolysis and α-glucosidase inhibitory were increased in the HT + US group compared to single pretreatment by 0.68%-17.34%, 12.69%-34.43% and 30.00%-53.46%. The peptide content and α-glucosidase inhibitory activity of CHPs could be maintained at 72.21 % and 57.97 % of the initial raw materials after in vitro digestion. Thus, the findings indicate that HT + US provides a feasible and efficient approach to can effectively enhance the enzymatic hydrolysis efficiency and hypoglycaemic efficacy of CHPs.

Preparation and Identification of Peptides with α-Glucosidase Inhibitory Activity from Shiitake Mushroom (Lentinus edodes) Protein

The shiitake mushroom is the most commonly cultivated edible mushroom in the world, and is rich in protein. This study aims to obtain the peptides with α-glucosidase inhibition activity from shiitake mushroom protein hydrolysate. The conditions of enzymatic hydrolysis of shiitake mushroom protein were optimized by response surface test. The results showed that the optimal conditions were as follows: the E/S was 3390 U/g, the solid-liquid ratio was 1:20, the hydrolysis temperature and time were 46 °C and 3.4 h, respectively, and the pH was 7. The active peptides were separated by gel filtration and identified by LC-MS/MS analysis and virtual screening. The results indicated that fourteen peptides were identified by LC-MS/MS. Among them, four new peptides (EGEPKLP, KDDLRSP, TPELKL, and LDYGKL) with the higher docking score were selected and chemically synthesized to verify their inhibition activity. The IC50 values of EGEPKLP, KDDLRSP, TPELKL, and LDYGKL for α-glucosidase inhibition activity ranged from 452 ± 36 μmol/L to 696 ± 39 μmol/L. The molecular docking results showed that the hydrogen bond and arene-cation bond were the two major interactions between four peptides and 2QMJ. The hydrogen bonds were crucial to the inhibition activity of α-glucosidase. The results indicate the potential of using the peptides from shiitake mushroom protein as functional food with α-glucosidase inhibition activity.

Comparison of the generation of α-glucosidase inhibitory peptides derived from prolamins of raw and cooked foxtail millet: In vitro activity, de novo sequencing, and in silico docking

Foxtail millet prolamin has been demonstrated to have anti-diabetic effects. In this study, we compared the generation of anti-α-glucosidase peptides derived from prolamins of raw and cooked foxtail millet (PRFM and PCFM). PRFM and PCFM hydrolysates (PRFMH and PCFMH) both exhibited α-glucosidase inhibitory activity. After ultrafiltration according to molecular weight (Mw), the fraction with Mw < 3 kDa in PCFMH (PCFMH_<3) showed higher α-glucosidase inhibitory activity than that in PRFMH (PRFMH_<3). The composition of α-glucosidase inhibitory peptides identified by de novo sequencing in PCFMH_<3 and PRFMH_<3 was compared by virtual screening, combining biological activity, net charge, grand average of hydropathicity (GRAVY), and key hydrophobic amino acids (Met, Pro, Phe, and Leu). We found that the proportion of peptides with excellent α-glucosidase binding force in PCFMH_<3 was higher than in PRFMH_<3. Overall, cooking may positively affect the generation of peptides that perform well in inhibiting α-glucosidase derived from foxtail millet prolamin.

Extraction, bioactive function and application of wheat germ protein/peptides: A review

The aging population and high incidence of age-related diseases are major global societal issues. Consuming bioactive substances as part of our diet is increasingly recognized as essential for ensuring a healthy life for older adults. Wheat germ protein has a reasonable peptide structure and amino acid ratio but has not been fully utilized and exploited, resulting in wasted wheat germ resources. This review summarizes reformational extraction methods of wheat germ protein/peptides (WGPs), of which different methods can be selected to obtain various WGPs. Interestingly, except for some bioactive activities found earlier, WGPs display potential anti-aging activity, with possible mechanisms including antioxidant, immunomodulatory and intestinal flora regulation. However, there are missing in vitro and in vivo bioactivity assessments of WGPs. WGPs possess physicochemical properties of good foamability, emulsification and water retention and are used as raw materials or additives to improve food quality. Based on the above, further studies designing methods to isolate particular types of WGPs, determining their nutritional and bioactive mechanisms and verifying their activity in vivo in humans are crucial for using WGPs to improve human health.

Identification and Molecular Binding Mechanism of Novel α-Glucosidase Inhibitory Peptides from Hot-Pressed Peanut Meal Protein Hydrolysates

Hot-pressed peanut meal protein hydrolysates are rich in Arg residue, but there is a lack of research on their α-glucosidase inhibitory activity. In this study, different proteases were used to produce hot-pressed peanut meal protein hydrolysates (PMHs) to evaluate the α-glucosidase inhibitory activity. All PMHs showed good α-glucosidase inhibitory activity with the best inhibition effect coming from the dual enzyme system of Alcalase and Neutrase with an IC₅₀ of 5.63 ± 0.19 mg/mL. The fractions with the highest inhibition effect were separated and purified using ultrafiltration and cation exchange chromatography. Four novel α-glucosidase inhibitory peptides (FYNPAAGR, PGVLPVAS, FFVPPSQQ, and FSYNPQAG) were identified by nano-HPLC-MS/MS and molecular docking. Molecular docking showed that peptides could occupy the active pocket of α-glucosidase through hydrogen bonding, hydrophobic interaction, salt bridges, and π-stacking, thus preventing the formation of complexes between α-glucosidase and the substrate. In addition, the α-glucosidase inhibitory activity of PMHs was stable against hot, pH treatment and in vitro gastrointestinal digestion. The study demonstrated that PMHs might be used as a natural anti-diabetic material with the potential to inhibit α-glucosidase.

Optimization and Molecular Mechanism of Novel α-Glucosidase Inhibitory Peptides Derived from Camellia Seed Cake through Enzymatic Hydrolysis

In recent years, food-derived hypoglycemic peptides have received a lot of attention in the study of active peptides, but their anti-diabetic mechanism of action is not yet clear. In this study, camellia seed cake protein (CSCP) was used to prepare active peptides with α-glucosidase inhibition. The optimization of the preparation of camellia seed cake protein hydrolyzed peptides (CSCPH) was conducted via response surface methodology (RSM) using a protamex with α-glucosidase inhibition as an indicator. The optimal hydrolysis conditions were pH 7.11, 4300 U/g enzyme concentration, 50 °C hydrolysis temperature, and 3.95 h hydrolysis time. Under these conditions, the α-glucosidase inhibition rate of CSCPH was 58.70% (IC₅₀ 8.442 ± 0.33 mg/mL). The peptides with high α-glucosidase inhibitory activity were isolated from CSCPH by ultrafiltration and Sephadex G25. Leu-Leu-Val-Leu-Tyr-Tyr-Glu-Tyr (LLVLYYEY) and Leu-Leu-Leu-Leu-Pro-Ser-Tyr-Ser-Glu-Phe (LLLLPSYSEF) were identified and synthesized for the first time by Liquid chromatography electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS) analysis and virtual screening with IC₅₀ values of 0.33 and 1.11 mM, respectively. Lineweaver-Burk analysis and molecular docking demonstrated that LLVLYYEY was a non-competitive inhibitor of α-glucosidase, whereas LLLLPSYSEF inhibited α-glucosidase, which displayed a mixed inhibition mechanism. The study suggests the possibility of using peptides from Camellia seed cake as hypoglycaemic compounds for the prevention and treatment of diabetes.

Acid-Resistant Mesoporous Metal-Organic Frameworks as Carriers for Targeted Hypoglycemic Peptide Delivery: Peptide Encapsulation, Release, and Bioactivity

Oral administration of bioactive peptides with α-glucosidase inhibitory activities is a promising strategy for diabetes mellitus. The wheat germ peptide Leu-Asp-Leu-Gln-Arg (LDLQR) has been previously proven to inhibit the activity of α-glucosidase efficiently. However, it is still difficult to transport the peptide to the intestine completely due to the harsh condition of the stomach. Herein, an acid-resistant zirconium-based metal-organic framework, NU-1000, was used to immobilize LDLQR with a high encapsulation capacity (92.72%) and encapsulation efficiency (44.08%) in only 10 min. The in vitro release results showed that the acid-stable NU-1000 not only effectively protected LDLQR from degradation in the presence of stomach acid and pepsin effectively but also ensured the release of encapsulated LDLQR under simulated intestinal conditions. Furthermore, LDLQR@NU-1000 could slow down the elevated blood sugar caused by maltose in mice and the area under blood sugar curve decreased by almost 20% when compared with the control group. The inflammatory factor (IL-1β, IL-6) in vivo and cell growth in vitro were almost the same between NU-1000 treatment and normal control groups. This study indicates NU-1000 is a promising vehicle for targeted peptide-based bioactive delivery to the small intestine.

Rapid Screening of Novel Dipeptidyl Peptidase-4 Inhibitory Peptides from Pea (Pisum sativum L.) Protein Using Peptidomics and Molecular Docking

Pea protein hydrolysates (PPHs) possess good hypoglycemic effects; however, their dipeptidyl peptidase-4 (DPP-4) inhibitory activity is poorly understood, and none of the DPP-4 inhibitory peptides have been identified from PPHs. This paper aims to rapidly screen these peptides from PPHs by combining peptidomics and molecular docking. In this study, 543 peptides were identified by peptidomics, and four peptides (IPYWTY, IPYWT, LPNYN, and LAFPGSS) with DPP-4 half-maximal inhibitory concentration (IC50) values <100 μM were screened for the first time. Significantly, peptide IPYWTY exhibited the most potent DPP-4 inhibitory activity (IC50 = 11.04 μM) mainly because it formed hydrophobic interactions with the S1 pocket in DPP-4. These results indicated that combining peptidomics and molecular docking is an effective strategy for rapidly screening DPP-4 inhibitory peptides.

Isolation, Identification, and Immunomodulatory Mechanism of Peptides from Lepidium meyenii (Maca) Protein Hydrolysate

Maca is a protein-enriched edible plant with immunomodulatory activity. However, the role of proteins in the immunomodulatory activity of maca is unclear. In this study, peptide products of maca proteins obtained through in vitro gastrointestinal digestion were isolated and purified, and the immunomodulatory activities of these peptides were assessed in macrophages (RAW 264.7 cells). The results show that the maca protein hydrolysate enhanced the phagocytic capacity and NO, TNF-α, and IL-6 secretion of RAW 264.7 cells. Forty-five peptides from known proteins of maca or the cruciferous family were identified by ultraperformance liquid chromatography-tandem mass spectrometry in the hydrolysate, and the peptide RNPFLP exhibited the strongest immunomodulatory activity. Antibody blocking, siRNA, pathway inhibitors, and western blot assays showed that RNPFLP-activated RAW 264.7 cells through the NF-κB and MAPK signaling pathways mediated by TLR2 and TLR4 receptors. An analysis of the structure-activity relationship showed that the N₉-H₆₀ active site in arginine plays an important role in the immunomodulatory activity of RNPFLP. This study provides a new understanding of the immunomodulatory activity of maca.