Extraction Of Peptides Research Articles

MDTL-ACP: Anticancer Peptides Prediction Based on Multi-Domain Transfer Learning.

Anticancer peptides (ACPs) have emerged as one of the most promising therapeutic agents for cancer treatment. They are bioactive peptides featuring broad-spectrum activity and low drug-resistance. The discovery of ACPs via traditional biochemical methods is laborious and costly. Accordingly, various computational methods have been developed to facilitate the discovery of ACPs. However, the data resources and knowledge of ACPs are still very scarce, and only a few of them are clinically verified, which limits the competence of computational methods. To address this issue, in this paper, we propose an ACP prediction model based on multi-domain transfer learning, namely MDTL-ACP, to discriminate novel ACPs from plentiful inactive peptides. In particular, we collect abundant antimicrobial peptides (AMPs) from four well-studied peptide domains and extract their inherent features as the input of MDTL-ACP. The features learned from multiple source domains of AMPs are then transferred into the target prediction task of ACPs via artificial neural network-based shared-extractor and task-specific classifiers in MDTL-ACP. The knowledge captured in the transferred features enhances the prediction of ACPs in the target domain. Experimental results demonstrate that MDTL-ACP can outperform the traditional and state-of-the-art ACP prediction methods. The source code of MDTL-ACP and the data used in this study are available at https://github.com/JunhangCao/MTL-ACP.

Antimicrobial activity of the crude peptide extracts from Blackfin sea catfish Arius jella Day, 1877

Antimicrobial activity of the crude peptide extracts from Blackfin sea catfish Arius jella Day, 1877

Effect of fermentation on antibacterial activity of milk from Vechur and Kasargod Dwarf cattle

The search for alternative therapeutics is on the rise on account of widespread bacterial resistance to numerous conventional antibiotics. Bioactive peptides produced by lactic acid bacteria found in natural sources such as fermented dairy products have attracted attention as a possible source of biotherapeutic peptides. Bioactive peptides released in fermented milk, on the other hand, is dependent on the proteolytic activities of the cultures used. As a result, this study was carried out to evaluate the effect of fermentation on antibacterial activity of milk from Vechur and Kasargod Dwarf cattle against pathogenic bacteria during 21-days storage period at 5°C. High-speed centrifugation was used to create water-soluble crude peptide extracts. The water-soluble peptides from Kasargod Dwarf and Vechur cattle by fermentation showed maximum inhibition against Escherichia coli NCIM2685 and Salmonella enterica ATCC 6017. The zone of inhibition measured ranges from 5mm to 11mm throughout the storage period. However, both did not show zone of inhibition against Bacillus cereus ATCC 10876 and Staphylococcus aureus ATCC 25923 during 21 days of storage at pH 7.4.

Effect of differential heat treatments on antibacterial activity of fermented goat milk

The present study was conducted to evaluate the effect of three different temperatures on the antibacterial potential of fermented goat milk.Goat milk is one of the naturalfoods to complete perfection.Bioactive peptides, the specific protein fragments that have a positive impact on body functions, can be produced during milk fermentation. Thanks to the starter cultures’ proteolytic activity.Fresh pooled goat milk sample collected was divided into four lots. One set was used for raw milk analysis and the remaining three were subjected to heat treatment at three different timetemperature combinations namely;72°C for 15 sec, 85°C for 10 min, and 121° C for 15 min. These samples were cooled immediately to 42ºC, inoculated with 0.04 % DVS yogurt culture,incubated at 42º C for 4 hrs, and then stored at 5±2°C for 21 days for storage studies. The analysis was carried out at 7-day intervals. An agar well diffusion assay was performed to assess the inhibitory activity ofWater-soluble peptide extracts (WSPE) of these samples against Bacillus cereus ATCC 10876, Escherichia coli NCIM 2685, Salmonella enterica ATCC 6017, and Staphylococcus aureus ATCC 25923. The milk that was heated to 85°C for 10 min before fermentation showed the highest antibacterial activity against E.coli during the 7th and 14th day of storage, withthe zone of inhibition measuredat 17±0.433mm and 21±0.55mm respectively.Thus, it can be concluded that milk heated at 85°C for 10 min had better antibacterial activity than the other two treatments.

Extraction, identification and anti-photoaging activity evaluation of collagen peptides from silver carp (Hypophthalmichthys molitrix) skin

Biologically active peptides are particularly important for anti-photoaging studies. In this study, silver carp (Hypophthalmichthys molitrix) skin collagen polypeptide (SCSCP) with collagenase inhibition activity was obtained by optimizing the enzymatic hydrolysis process. Fourier-transform infrared spectroscopy, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, and liquid-liquid mass spectrometry were used to analyze the secondary structure, molecular weight distribution and characteristics of peptides, respectively. The effects of SCSCP on the proliferation of mouse fibroblasts (L929) and secretion of matrix metalloproteinase-1 (MMP-1) after UVB irradiation were also detected. Process-optimized SCSCP inhibited collagenase activity up to 54.47%. In SCSCP, α-helical and β-folded structures accounted for 17.70% and 22.65%, respectively. The relative molecular weights of SCSCP were more widely distributed below 1600 Da, with higher response values at 665.93 and 980.95 Da. The molecular weights of the characteristic peptides were 358.68–863.89 Da, and the peptide sequences with anti-photoaging activity were GPPGPPGTPGPQ, SGLPGPIGPPGPR, and GLPGPIGPPGPR. SCSCP at 10 mg/mL concentration had high DPPH and hydroxyl radical scavenging activity, while 0.1 mg/mL SCSCP significantly restored UVB-induced L929 cell viability and inhibited MMP-1 secretion in L929 cells after UVB irradiation. These results indicate that SCSCP achieves anti-photoaging effects by scavenging DPPH and hydroxyl radicals and inhibiting MMP-1 secretion.

Bile acid-binding capacity of peptide extracts obtained from chicken blood hydrolysates using HPLC

Bile acids are involved in the modulation of various metabolic processes facilitating the biliary excretion of endogenous and exogenous cholesterol. The objective of this study was to determine the glycocholic acid binding capacity (BC) of chicken blood hydrolysates using an optimized RP-HPLC methodology. Samples were hydrolysed using a combination of five different enzymes. Alcalase and Protamex hydrolysates presented the highest BC, with mean values of 20.09% and 20.61%, respectively. Subsequently, both hydrolysates were ultrafiltered to obtain fractions >10 kDa, between 10 and 3 kDa, and <3 kDa, and the highest BC values were obtained for peptide fractions >10 kDa. Finally, the protein fragments (MW > 10 kDa) potentially responsible for BC were identified by LC-MS/MS. The results confirmed the relation of BC with the molecular weight of the peptides generated, suggesting that certain protein fragments generated from chicken blood could contribute to a positive impact on health by interfering with cholesterol metabolism.

Controlling soft rot of postharvest chilli pepper (Capsicum annuum L.) by an antagonist Bacillus amyloliquefaciens S917: Efficacy and action mode

Pectobacterium carotovorum, the causal agent of soft rot, is responsible for significant economic damage in storage and transportation of postharvest chilli pepper. In this study, an antagonist S917, identified as Bacillus amyloliquefaciens based on the 16S rDNA sequence, was screened from 1400 strains for antagonistic activity towards Pectobacterium carotovorum subsp. brasiliense XC1 (Pcb XC1). The in vitro antibacterial result showed that cells and peptide extract of B. amyloliquefaciens S917 had good inhibitory activity against Pcb XC1. Based on draft genome sequences of B. amyloliquefaciens S917, five bacteriocins (Thusin_alpha, Thusin_beta2, Amylocyclicin, ComX1, LCI-like) were identified by BAGEL4 database and four antibacterial metabolites (Bacillaene, Macrolactin H, Bacilysin, Bacillibactin) were identified by antiSMASH database. The in vivo disease control result of chilli pepper showed that cells of B. amyloliquefaciens S917 performed better in reducing the rotting incidence and lesion diameter. Result of gas chromatography-ion mobility spectrometry (GC-IMS) showed that B. amyloliquefaciens S917 cells (BSC) treatment protected the original volatile aroma of chilli pepper. However, the control had richer volatile compounds related to soft rot, including methylbutanoate, dimethyl sulfide, methylbutanal, 3-methyl-2-butenal, pentan-1-ol, 3-methylbutan-1-ol, hexanol. Further, action mode of BSC was investigated. The number of green fluorescent protein labelled Pcb XC1 in chilli pepper was reduced by more than 99% after BSC treatment. Result of scanning electron microscopy also showed that BSC treatment prevented the damage of pepper epidermal structure caused by Pcb XC1. Moreover, the result of RNA-seq showed that BSC treatment triggered defense responses of chilli pepper. Pathways of plant pathogen interaction, phenylpropanoid biosynthesis and metabolism, plant hormone synthesis and signal transduction, MAPK signaling, WRKY transcription factor, and cell wall synthesis were activated. This study confirmed that B. amyloliquefaciens S917 can be used as an antagonist to control soft rot of postharvest chilli pepper.

Comparative transcriptomes of nine tissues for the Heilongjiang brown frog (Rana amurensis)

The Heilongjiang brown frog (Rana amurensis) is widely used in traditional Chinese medicine. In particular, the oviduct and skin have been developed into various health products. However, limited numbers of complete genomes of amphibian species have been reported, excluding the Heilongjiang brown frog. Here, the transcriptomes of 45 samples from the liver, spleen, heart, ovaries, thigh muscles, skin, oviduct, stomach and intestine of five Heilongjiang brown frog were reassembled and analyzed. A total of 1,085,532 unigenes with an average length of 676.6 bp and N50 of 722 bp were obtained. Comparative transcriptomics of different tissues detected tissue-specific expression. There were 3248 differentially expressed genes (DEGs) in the ovary, and the number of unique DEGs between the ovary and spleen was the largest. The results of DEGs enrichment showed there were many pathways and items related to protein synthesis and metabolism in the oviduct. The DEGs of the skin were enriched with many bacterial defense items, indicating that there were a large number of antimicrobial peptides in the skin. Thus, these were suitable as biological sources for the development and extraction of antimicrobial peptides. Through the assembly of transcriptome sequencing data and functional annotation of the Heilongjiang brown frog genome, this study provides reference materials for further exploring and utilizing functional gene resources of frogs and lays a foundation for medical research and the development of new products.

Extraction of bioactive peptides produced in probiotic yoghurt and determination of their biological activities

This research evaluated the proteolytic activity of Iranian and commercial probiotic strains (e.g., Bifidobacterium lactis, Lactobacillus acidophilus, and Lactobacillus casei) in yoghurt during 28 days of storage. Water-soluble peptides were extracted using high-speed centrifugation. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) methods were used to evaluate the bioactive activities of water-soluble peptide extract (WSPE). Antimutagenic and antibacterial activity against Staphylococcus aureus was investigated using the Ames test and agar gel diffusion method, respectively. There was a direct relationship between formation of bioactive peptides and degree of proteolysis. There was a significant difference between the probiotic and control samples. S. thermophilus + L. bulgaricus + Iranian strain of B. lactis had the highest antioxidant, antimutagenic and antibacterial activities. Therefore, Iranian B. lactis has a high potential for producing bioactive peptides having health benefits in commercial foods such as yoghurt, novel products and therapeutic peptides.

Structural and Functional Analysis of Peptides Derived from KEX2-Processed Repeat Proteins in Agaricomycetes Using Reverse Genetics and Peptidomics.

Bioactivities of fungal peptides are of interest for basic research and therapeutic drug development. Some of these peptides are derived from "KEX2-processed repeat proteins" (KEPs), a recently defined class of precursor proteins that contain multiple peptide cores flanked by KEX2 protease cleavage sites. Genome mining has revealed that KEPs are widespread in the fungal kingdom. Their functions are largely unknown. Here, we present the first in-depth structural and functional analysis of KEPs in a basidiomycete. We bioinformatically identified KEP-encoding genes in the genome of the model agaricomycete Coprinopsis cinerea and established a detection protocol for the derived peptides by overexpressing the C. cinerea KEPs in the yeast Pichia pastoris. Using this protocol, which includes peptide extraction and mass spectrometry with data analysis using the search engine Mascot, we confirmed the presence of several KEP-derived peptides in C. cinerea, as well as in the edible mushrooms Lentinula edodes, Pleurotus ostreatus, and Pleurotus eryngii. While CRISPR-mediated knockout of C. cinerea kep genes did not result in any detectable phenotype, knockout of kex genes caused defects in mycelial growth and fruiting body formation. These results suggest that KEP-derived peptides may play a role in the interaction of C. cinerea with the biotic environment and that the KEP-processing KEX proteases target a variety of substrates in agaricomycetes, including some important for mycelial growth and differentiation. IMPORTANCE Two recent bioinformatics studies have demonstrated that KEX2-processed repeat proteins are widespread in the fungal kingdom. However, despite the prevalence of KEPs in fungal genomes, only few KEP-derived peptides have been detected and studied so far. Here, we present a protocol for the extraction and structural characterization of KEP-derived peptides from fungal culture supernatants and tissues. The protocol was successfully used to detect several linear and minimally modified KEP-derived peptides in the agaricomycetes C. cinerea, L. edodes, P. ostreatus, and P. eryngii. Our study establishes a new protocol for the targeted search of KEP-derived peptides in fungi, which will hopefully lead to the discovery of more of these interesting fungal peptides and allow a further characterization of KEPs.

Antioxidant Effects of Modified-Release Peptide Extracts in Correcting Light Desynchronosis

This research was aimed at creating novel domestic medical preparations with a modified release of active peptide substances obtained from renewable sources of biological materials. These preparations can be used for the purposes of pharmacological correction of desynchronosis by the action of biologically active substances on the processes of lipid peroxidation and antioxidant protection of cells in order to increase the body's resistance to the negative effects of various stress factors. The conducted studies have confirmed the efficacy of modified-release peptide extracts when correcting the body's oxidative status in various types of desynchronosis.

Characteristics of the enzyme-induced release of bitter peptides from wheat gluten hydrolysates.

Bitter peptides in the enzymatic hydrolysates were prepared and purified from wheat gluten using aqueous ethanol solutions and macroporous resin, which has opened a new road for the extraction and separation of bitter peptides. This report contains the release regularity of bitter peptides and the factors affecting the change of bitter intensity during enzymatic hydrolysis, providing a scientific basis for the research on debitterizing method. In this study, the effects of different degrees of hydrolysis (DH) and enzyme active sites on the bitter peptide content and bitter taste thresholds were discussed. The relationship between amino acid composition, molecular weight distribution, surface hydrophobicity and bitter taste thresholds was extensively researched. The results showed the exposure of hydrophobic amino acids and the bitterness intensity of the hydrolysates increased as the DH increased, and the bitterness of wheat gluten hydrolysates (WGHs) hydrolyzed by Alcalase was stronger than that of Trypsin. According to correlation analysis, the proportion of total hydrophobic amino acid is the first factor that affects the sensory properties of bitter peptide, and the release content of bitter peptides and the content of total bitter amino acids are the second, following by the content of peptide in the molecular weight range of 500–1,000 Da and the surface hydrophobicity. The amino acid sequence of bitter peptides from WGHs were identified and predicted using high performance liquid chromatography-mass spectrometry (HPLC-MS/MS) and bioinformatics. It was found that the molecular weight of most of the peptides was below 1,500 Da, and the Q value was higher than 5.86 kJ/mol.

Computer-aided design of proline-rich antimicrobial peptides based on the chemophysical properties of a peptide isolated from Olivancillaria hiatula

The chemophysical properties of a peptide isolated from Olivancillaria hiatula were combined with computational tools to design new antimicrobial peptides (AMPs). The in silico peptide design utilized arbitrary sequence shuffling, AMP sequence prediction and alignments such that putative sequences mimicked those of proline-rich AMPs (PrAMPs) and were potentially active against bacteria. Molecular modelling and docking experiments were used to monitor peptide binding to some intracellular targets like bacteria ribosome, DnaK and LasR. Peptide candidates were tested in vitro for antibacterial and antivirulence activities. Chemophysical studies of peptide extract suggested hydrophobic, acidic and proline-rich peptide properties. The amino acid signature of the extract matched that of AMPs that inhibit intracellular targets. Two of the designed PrAMP peptides (OhPrP-3 and OhPrP-5) had high affinity for the ribosome and DnaK. OhPrP-1, 2 and 4 also had favorable interactions with the biomolecular targets investigated. Peptides had bactericidal activity at the minimum inhibitory concentration against Pseudomonas aeruginosa. The designed peptides docked strongly to LasR suggesting possible interference with quorum sensing, and this was corroborated by in vitro data where sub-inhibitory doses of all peptides reduced pyocyanin and pyoverdine expression. The designed peptides can be further studied for the development of new anti-infective agents.

Optimized Chemical Extraction Methods of Antimicrobial Peptides from Roots and Leaves of Extremophilic Plants: Anthyllis sericea and Astragalus armatus Collected from the Tunisian Desert.

Extraction methods depend mainly on the chemical nature of the extracted molecule. For these reasons, the selection of the extraction medium is a vital part of obtaining these molecules. The extraction of antimicrobial peptides (AMPs) from extremophile plants is important because of its potential pharmaceutical applications. This work focused on the evaluation of several solvents for the extraction of AMPs from the following two extremophile plants: Astragalus armatus and Anthyllis sericea from southern Tunisia. In order to identify the most efficient solvents and extraction solutions, we used sulfuric acid, dichloromethane, phosphate buffer, acetic acid and sodium acetate, and we tested them on leaves and roots of both the studied plants. The extracts obtained using sulfuric acid, dichloromethane and phosphate buffer extraction did not show any antimicrobial activity, whereas the acetic acid and sodium acetate extracts led to growth inhibition of some of the tested bacterial strains. The extracts of leaves and roots of An. sericea and As. armatus obtained by acetic acid and sodium acetate were proven to be active against Gram-positive bacteria and Gram-negative bacteria. Therefore, the most appropriate solvents to use for antimicrobial peptide extraction from both plants are acetic acid and sodium acetate.

Application of High Pressure Processing on Ultrasonically Treated Extract from Wild Bitter Gourd

Wild bitter gourd extracts, such as saponins, polysaccharides, and peptides, could be used to adjust blood sugar. The objective of this research was to explore the use of high pressure processing (HPP) for sterilization and acceleration of enzyme hydrolysis in the ultrasonic preparation of peptide extracts from wild bitter gourd. The results showed that the wild bitter gourd powder could be extracted via ultrasonic processing with water at 70 °C for only 20 min with a solid to liquid ratio of 1:20 to obtain the total protein content of 1.514 mg/g. The two sterilization methods for wild bitter gourd extract treated with papaya enzyme—for 2 h in the traditional autoclave at 121 °C for 15 min, or under HPP 300 MPa for 5 min—showed no significant effect on protein content, and both sterilization methods were effective. However, the extract sterilized with HPP had a significantly higher ability to scavenge DPPH free radicals. In addition, HPP (300 MPa for 5 min), combined with papaya enzyme to hydrolyze the wild bitter gourd extract, simultaneously pasteurized the extract and acquired the peptides from the wild bitter gourd extract Therefore, the ultrasonic extraction of wild bitter gourd, combined with HPP and enzyme hydrolysis, could greatly shorten the operation time (to only 5 min) for extracting the active peptides.

Peptide-rich extracts from spent yeast waste streams as a source of bioactive compounds for the nutraceutical market

Spent yeast is one of the main fermentation process by-products and several bioactive ingredients have been extracted from it, such as mannans and β-glucans. These extraction processes generate waste streams rich in protein, that can still be used to produce peptide-rich extracts. This work describes the use of a scalable and low-cost process to obtain yeast peptide extracts in a circular economy concept. Peptide fractions produced contained 48.3 to 86.4% of protein (w/w) and essential amino acids amounts higher than those defined by FAO and WHO references. Regarding their bioactive properties, extracts exhibited strong antihypertensive and antioxidant activities. Furthermore, an inhibition of 62.0–71.3% in HMG-CoA reductase was observed, a feature hereby described for the first time, thus stating the cholesterol-lowering capacity of yeast peptides. In conclusion, due to their combined nutritional and bioactive characteristics, the produced yeast peptide extracts are good candidates for dietary supplementation and functional foods.

Single and Co-Cultures of Proteolytic Lactic Acid Bacteria in the Manufacture of Fermented Milk with High ACE Inhibitory and Antioxidant Activities

In this study, single and co-cultures of proteolytic Lactobacillus delberueckii subsp. bulgaricus ORT2, Limosilactobacillus reuteri SRM2 and Lactococcus lactis subsp. lactis BRM3 isolated from different raw milk samples were applied as starter cultures to manufacture functional fermented milks. Peptide extracts from fermented milk samples were evaluated after fermentation and 7 days of cold storage for proteolytic, angiotensin-converting enzyme (ACE) inhibitory and antioxidant activity by different methods including 2, 2′-diphenyl-1-picrylhydrazyl (DPPH), ferric-reducing antioxidant power (FRAP), OH-radical scavenging, and total antioxidant (molybdate-reducing activity). The highest proteolysis was found in milk fermented by co-cultures of three strains. Fermentation with the mentioned bacteria increased ACE inhibitory and antioxidant activity of the final products which were dependent on peptide concentration. The crude peptide extract obtained from fermented milk with triple co-culture showed the highest ACE inhibitory activity (IC50 = 0.61 mg/mL) which was reduced after 7 days of cold storage (IC50 = 0.78 mg/mL). Similar concentration-dependent activities were found in antioxidant activity at different antioxidant assays. Overall, high proteolytic activity resulted in increased ACE inhibitory and antioxidant activities, but the highest activity was not necessarily found for the samples with the highest proteolytic activity. The results of this study suggest the potential of using co-cultures of L. delberueckii subsp. bulgaricus, L. reuteri and L. lactis subsp. Lactis to manufacture antihypertensive fermented milk.

Reconfiguration of Gut Microbiota and Reprogramming of Liver Metabolism with Phycobiliproteins Bioactive Peptides to Rehabilitate Obese Rats.

Phycobiliproteins (derived from Arthrospira platensis) bioactive peptide extracts (PPE) possess multiple pharmacological effects in the mitigation of human metabolic disorders. The role of PPE in the treatment of diet-induced obesity and the understanding of the underlying mechanism between the gut microbiome and metabolic blood circulation for obese patients remains poorly understood. In this study, we showed that PPE attenuated obesity by reducing body weight, and ameliorated glucose and lipid indexes in serum. In particular, PPE is postulated to mitigate liver steatosis and insulin resistance. On the other hand, dietary treatment with PPE was found to “reconfigure” the gut microbiota in the way that the abundances were elevated for Akkermansia_muciniphila, beneficial Lactobacillus and Romboutsia, SCFA-producing species Faecalibacterium prausnitzii, Lachnospiraceae_bacterium, Clostridiales_bacterium, probiotics Clostridium sp., Enterococcus faecium, and Lactobacillus_johnsonii, while the abundance of Firmicutes was reduced and that of Bacteroidetes was increased to reverse the imbalance of Firmicutes/Bacteroidetes ratio. Finally, the metabolomics of circulating serum using UHPLC-MS/MS illustrated that PPE supplementation indeed promoted lipid metabolism in obese rats. As summary, it was seen that PPE reprogrammed the cell metabolism to prevent the aggravation of obesity. Our findings strongly support that PPE can be regarded as a potential therapeutic dietary supplement for obesity.

Antimicrobial and Functional Properties of Duckweed (Wolffia globosa) Protein and Peptide Extracts Prepared by Ultrasound-Assisted Extraction.

Wolffia globosa is an interesting alternative plant-based protein source containing up to 40% protein dry weight. Dried duckweed protein extract (PE) was obtained using ultrasound-assisted extraction (UAE) before isoelectric precipitation (pH 3.5) to yield protein concentrate (PC) and protein solution (PS). The PC was hydrolyzed using Alcalase enzyme to obtain protein concentrate hydrolysate (PCH). Among all fractions, PCH exhibited antimicrobial properties by decreasing populations of Vibrio parahaemolyticus and Candida albicans at 0.43 ± 1.31 log reduction (66.21%) and 3.70 ± 0.11 log reduction (99.98%), respectively. The PE and PS also showed high solubilities at pH 8 of 90.49% and 86.84%, respectively. The PE demonstrated the highest emulsifying capacity (EC) (71.29%) at pH 4, while the highest emulsifying stability (ES) (~98%) was obtained from the PE and PS at pH 6 and pH 2, respectively. The major molecular weights (Mw) of the PE, PC, PCH and PS were observed at 25, 45, 63 and 100 kDa, with a decrease in the Mw of the PCH (<5 kDa). The PCH contained the highest total amino acids, with aspartic acid and glutamic acid being the major components. The results revealed the antimicrobial and functional properties of duckweed protein and hydrolysate for the first time and showed their potential for further development as functional food ingredients.

Formation and inhibition mechanism of novel angiotensin I converting enzyme inhibitory peptides from Chouguiyu

Angiotensin I converting enzyme (ACE) inhibitory peptides from fermented foods exhibit great potential to alleviate hypertension. In this study, the peptide extract from Chouguiyu exhibited a good inhibition effect on ACE, and the inhibition rate was significantly enhanced after fermentation for 8 days. The ACE inhibitory peptides were further identified, followed by their inhibition and formation mechanisms using microbiome technology and molecular docking. A total of 356 ACE inhibitory peptides were predicted using in silico, and most ACE inhibitory peptides increased after fermentation. These peptides could be hydrolyzed from 94 kinds of precursor proteins, mainly including muscle-type creatine kinase, nebulin, and troponin I. P1 (VEIINARA), P2 (FAVMVKG), P4 (EITWSDDKK), P7 (DFDDIQK), P8 (IGDDPKF), P9 (INDDPKIL), and P10 (GVDNPGHPFI) were selected as the core ACE inhibitory peptides according to their abundance and docking energy. The salt bridge and conventional hydrogen bond connecting unsaturated oxygen atoms in the peptides contributed most to the ACE inhibition. The cleavage proteases from the microbial genera in Chouguiyu for preparing these 7 core ACE inhibitory peptides were further analyzed by hydrolysis prediction and Pearson's correlation. The correlation network showed that P7, P8, and P9 were mainly produced by the proteases from LAB including Lactococcus, Enterococcus, Vagococcus, Peptostreptococcus, and Streptococcus, while P1, P2, P4, and P10 were mainly Produced by Aeromonas, Bacillus, Escherichia, and Psychrobacter. This study is helpful in isolating the proteases and microbial strains to directionally produce the responding ACE inhibitory peptides.