Rich Source Of Bioactive Peptides Research Articles

Rapeseed protein-derived peptides, LY, RALP, and GHS, modulates key enzymes and intermediate products of renin\u2013angiotensin system pathway in spontaneously hypertensive rat

Rapeseed proteins are a rich source of bioactive peptides. LY, RALP and GHS were previously identified from rapeseed protein hydrolysates as potent ACE and renin inhibiting peptides. In this study, the rapeseed peptides were individually evaluated for their molecular mechanisms and regulatory effects on components of the renin–angiotensin system in spontaneously hypertensive rats (SHR), including the mRNA and/or protein levels of angiotensin-converting enzyme (ACE), renin, ACE2, angiotensin II and angiotensin-(1–7) in myocardial tissues. Oral administration of 30 mg peptides/kg body weight every 2 days for five weeks significantly decreased the systolic blood pressure and the myocardial mRNA and protein levels of ACE and renin in SHR. LY, RALP and GHS also increased the expression of ACE2, angiotensin-(1-7) and Mas receptor levels, which may have mediated their antihypertensive activity. Dipeptide LY also inhibited angiotensin II protein expression in the heart tissue. Taken together, the finding demonstrates the multi-target physiological effects of the rapeseed peptides, beyond ACE and renin inhibition, which enhances knowledge of the antihypertensive mechanisms of food protein-derived peptides.

Identification of

Skins of anurans (frogs and toads) are rich sources of bioactive peptides. However, the peptides secreted by the skin glands of Bufo gargarizans, the most common toad in China, remained unexplored to date. Here, a strategy combines LC–MS/MS, RNA sequencing and bioinformation analysis was applied to unravel the peptides in the Bufo gargarizans secretions. Data-dependent LC–MS/MS acquisitions of intact peptides followed by automated chromatographic alignment, De novo analysis, database and homology searches with manual validations showed that the venom is composed by 939 features, with masses ranging from 0.7–4 kDa. These peptides derived from 85 proteins were identified using the PEAKS software with acquired MS and MS/MS spectra of Venenum Bufonis against the house-built protein database using De novo RNA sequencing, while only 23 peptides from 8 proteins were found when searching known amphibian database. Moreover, it was found that many peptides with high abundance in Venenum Bufonis derived from proteolytic processing of a larger precursor protein, named as CL4590. Molecular cloning was applied to validate a short domain of CL4590 to evident the accuracy of these obtained sequences. Although the bioactivities of peptides identified by MS/MS are unknown, the next function annotation showed that they may involve in the cell killing, immune and metabolic process, antioxidant activity and antimicrobial actions. Therefore, the peptidomics analysis on Bufo gargarizans discover abundant novel toad peptides which broaden our horizons on the secretion multiplicity and supplied an assortment of pharmacological candidates.

High-Accuracy Mass Spectrometry Based Screening Method for the Discovery of Cysteine Containing Peptides in Animal Venoms and Toxins.

Venom and toxin samples derived from animal origins are a rich source of bioactive peptides. A high proportion of bioactive peptides that have been identified in venom contain one or more disulfide bridges, which are thought to stabilize tertiary structure, and therefore influence the peptides' specificity and activity. In this chapter, we describe a label-free mass spectrometry-based screening workflow specifically to detect peptides that contain inter- and intramolecular disulfide bonds, followed by elucidation of their primary structure. This method is based on the determination of the normalized isotope shift (NIS) and the normalized mass defect (NMD) of peptides, two parameters which are heavily influenced by the presence of sulfur in a peptide, where cysteines are the main contributing residues. Using ant defensive secretions as an example, we describe the initial fractionation of the venom on strong cation exchange followed by nanoflow HPLC and mass spectrometry. High resolution zoom scan spectra of high-abundance peptides are acquired, allowing an accurate determination of both monoisotopic and average mass, which are essential for calculation of NMD and NIS. Candidate peptides exhibiting relative low NMD and high NIS values are selected for targeted de novo sequencing. By fine-tuning the collision energy for optimal fragmentation of each selected precursor ions, the full sequence of several novel inter- and intramolecular disulfide bond containing ant defensive peptides can be established.

Evaluation of the in vitro antimicrobial activity of selected Saudi scorpion venoms tested against multidrug-resistant micro-organisms.

Scorpion venoms are a rich source of bioactive peptides with promising clinical value that may lead to the discovery and development of new drugs. The present study was designed to evaluate the in vitro antimicrobial activities of the venoms extracted from three medically important Saudi scorpions (Androctonus crassicauda, Androctonus bicolor and Leiurus quinquestriatus). Antimicrobial assays were performed using a microplate growth inhibition assay against 10 multidrug-resistant (MDR) micro-organisms (4 Gram-negative bacteria, 2 Gram-positive bacteria and 4 fungi and yeasts) at concentrations ranging from 0 to 20mg/mL of each venom. Following qualitative analysis, dose-response assays were performed for bacterial and fungal killing curves using the MTT colorimetric assay. Among the three tested scorpion venoms, only L. quinquestriatus venom showed significant broad-spectrum antimicrobial activity in a dose-dependent manner from 5 to 20mg/mL. Leiurus quinquestriatus venom inhibited the growth and survival of MDR Escherichia coli (55.2%), Acinetobacter baumannii (50.6%), Klebsiella pneumoniae (35.1%), Pseudomonas aeruginosa (31.3%), Staphylococcus aureus (36.4%), Enterococcus faecalis (47.6%), Candida albicans (31.2%) and Candida glabrata (39.0%), whereas no significant activity against Fusarium oxysporum and Aspergillus flavus was observed. In contrast, the venoms of A. crassicauda and A. bicolor did not show noticeable antimicrobial activity against any of the tested organisms. The findings of the current study demonstrate that L. quinquestriatus venom possesses antimicrobial activity and thus can be used as a template for designing and development of novel antimicrobial drugs.

Novel short antimicrobial peptide isolated from Xenopus laevis skin.

A rich source of bioactive peptides, including a large number of antimicrobial peptides, has been found in amphibian skin. In this study, a novel short antimicrobial peptide was purified from Xenopus laevis skin and characterised through reversed-phase high-performance liquid chromatography, Edman degradation and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. The peptide was composed of six amino acids with a sequence of DEDLDE and thus named X. laevis antibacterial peptide-P2 (XLAsp-P2). Transmission electron microscopy revealed that this peptide showed potential antimicrobial abilities against bacteria by damaging the bacterial cell membrane. XLAsp-P2 maybe inhibit bacterial growth by binding to the microbial genomic DNA. The peptide also exhibited a weak haemolytic activity against rabbit red blood cells. Therefore, XLAsp-P2 is a novel short anionic antibacterial peptide with broad activities. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Potential Applications of Food Derived Bioactive Peptides in Management of Health

Recently the rise in noncommunicable diseases and side effects of drugs has promoted the research in food components with biologically active molecules. These bioactive components are vital in reducing and regulating the onset of such chronic degenerative diseases. Many food derived peptides are biologically active fragments encrypted within the primary protein sequence in nascent (inactive) form, hence also called ‘cryptides’. These bioactive peptides range in size from 2 to 50 amino acids. They function beyond their basic nutritional benefits. Upon oral administration, these peptides play various roles such as opiate like, antioxidative, immunomodulatory, antihypertensive, hypocholesterolemic, mineral binding, antiobesity and antimicrobial. Both animal and plant proteins are rich sources of bioactive peptides having specific physiological and biochemical functions. Digestion of proteins in vivo or in vitro produces free amino acids and peptides which enter circulatory system and exert systemic effect. Bioactive peptides can be produced in vivo through gastrointestinal digestion whereas in vitro through chemical processing of food proteins with acid, alkali, heat and enzymatic hydrolysis either by digestion or fermentation. Protein hydrolysates being rich source of bioactive peptides can serve as an alternative to intact protein and elemental formula in the development of functional foods.

Peptides-Derived from Thai Rice Bran Improves Endothelial Function in 2K-1C Renovascular Hypertensive Rats.

In recent years, a number of studies have investigated complementary medical approaches to the treatment of hypertension using dietary supplements. Rice bran protein hydrolysates extracted from rice is a rich source of bioactive peptides. The present study aimed to investigate the vasorelaxation and antihypertensive effects of peptides-derived from rice bran protein hydrolysates (RBP) in a rat model of two kidney-one clip (2K-1C) renovascular hypertension. 2K-1C hypertension was induced in male Sprague-Dawley rats by placing a silver clip around the left renal artery, whereas sham-operated rats were served as controls. 2K-1C and sham-operated rats were intragastrically administered with RBP (50 mg·kg−1 or 100 mg·kg−1) or distilled water continuously for six weeks. We observed that RBP augmented endothelium-dependent vasorelaxation in all animals. Administration of RBP to 2K-1C rats significantly reduced blood pressure and decreased peripheral vascular resistance compared to the sham operated controls (p < 0.05). Restoration of normal endothelial function and blood pressure was associated with reduced plasma angiotensin converting enzyme (ACE), decreased superoxide formation, reduced plasma malondialdehyde and increased plasma nitrate/nitrite (p < 0.05). Up-regulation of eNOS protein and down-regulation of p47phox protein were found in 2K-1C hypertensive rats-treated with RBP. Our results suggest that RBP possesses antihypertensive properties which are mainly due to the inhibition of ACE, and its vasodilatory and antioxidant activity.

Masking of bitterness in dairy protein hydrolysates: Comparison of an electronic tongue and a trained sensory panel as means of directing the masking strategy

Sodium caseinate hydrolysates (NaCaHs) are known to be a rich source of bioactive peptides but are also known to have a bitter taste which can make them difficult to incorporate into foods. The objective of the study was to identify whether a commercially available electronic tongue (e-tongue) could be used to identify sweeteners and flavours which reduce bitterness perception in model beverages containing NaCaHs. The two NaCaHs analysed in this study were found to be strongly bitter, the sensory panel found sucralose to be the most effective sweetener, reducing bitterness by a minimum of 39% at the lowest concentration assessed, 0.017% w/w, and the flavour vanilla was the most effective flavouring for further reducing bitterness in a sweetened model beverage. The e-tongue was found to be an effective tool for measuring the reduction of bitterness in of NaCaHs due to different sweeteners but not for evaluating the effect of flavourings in the model beverage. The results also showed good agreement between the e-tongue and sensory panel in the measurement of bitterness and sweetness in sweetened NaCaHs suggesting that the e-tongue maybe a useful device for the selection of sweeteners as bitterness masking agents in NaCaHs.

Evaluation of two sub-2 μm stationary phases, core–shell and totally porous monodisperse, in the second dimension of on-line comprehensive two dimensional liquid chromatography, a case study: Separation of milk peptides after expiration date

Milk is a rich source of bioactive peptides of great interest for their healthy properties. These peptides are usually encrypted in the sequences of proteins and are released after time dependent proteolysis as very complex hydrolysates. In order to separate and identify the bioactive sequences, we developed an on-line comprehensive two dimensional liquid chromatography approach using the high performance combined with the ultra high performance conditions. A microbore reversed phase (C18 silica, 5μm) column was employed in first dimension, while, in second dimension, two different UHPLC columns, packed with C18 silica, were tested: a new column based on monodisperse sub-2μm fully porous particles with high surface area (50mm×3.0mm, 1.9μm d.p., from Supelco), and a column based on sub-2μm core–shell particles (50mm×3.0mm, 1.7μm d.p, from Phenomenex®). Both set-ups were compared, showing high peak capacity values with respect to a high efficiency monodimensional method, maintaining the same analysis time. Satisfactory selectivity was obtained through the use of different pH between the two dimension, while a very fast continuous shifted gradient in second dimension ensured a good employment of the 2D separation space.

Selective enrichment of bioactive properties during ultrafiltration of a tryptic digest of β-lactoglobulin

Whey proteins are rich sources of bioactive peptides which may play a role in the dietary management of chronic diseases. Fractionation via ultrafiltration (UF) was investigated for the enrichment of antioxidant, dipeptidyl peptidase IV (DPP-IV) and angiotensin converting enzyme (ACE) inhibitory activity in a tryptic hydrolysate of β-lactoglobulin (β-Lg TH). UF processing selectively enhanced the biofunctional properties of β-Lg TH with the permeate obtained using a 1 kDa polyethersulfone (HFP-1) membrane having highest in vitro multifunctional bioactivity. Compared to β-Lg TH, the antioxidant activity was 1.7-fold higher (46,765 ± 2504 vs. 77,251 ± 5124 µmol Trolox equivalent/100 g dw; P < 0.05), DPP-IV half maximal inhibitory concentration (IC50) decreased threefold (1.6 ± 0.31 vs. 0.53 ± 0.05 mg/mL; P < 0.05) and there was a twofold reduction in ACE IC50 (0.131 ± 0.005 vs. 0.068 ± 0.018 mg/mL; P < 0.05). The multifunctional peptide VAGTWY, β-Lg f(15–20) was shown to have potent antioxidant activity (5.63 µmol TE/µmol peptide). Two new ACE inhibitory peptides, IIAEK and IPAVFK, having IC50 values of 63.7 ± 7.22 and 144.8 ± 25.3 μM, respectively, were also identified in β-Lg TH. This study demonstrates the multifunctional bioactive properties of a β-Lg TH and its associated UF fractions.

An overview of “omic” analytical methods applied in bioactive peptide studies

Nowadays, there is an increased interest in health-promoting functional foods, whereby consumers hold higher expectations of health-promoting benefits beyond basic nutrition. Dietary proteins provide a rich source of bioactive peptides, which are hidden in a latent state within the native protein, requiring enzymatic proteolysis for their release. Bioactive peptides can be produced during in vivo gastrointestinal digestion and/or food processing. Lactic acid bacteria are among the most widely microorganisms used as starter cultures for the production of fermented foods, and through their proteolytic system, they contribute to the release of bioactive peptides from dietary proteins. In vitro and in vivo studies demonstrated several biological functions attributed to bioactive peptides, such as antimicrobial, immunomodulatory, enhancement of mineral absorption, antithrombotic, antihypertensive, opioid and antioxidant activities. The great complexity and the wide dynamic range of relative peptide abundance in these products severely challenge the capabilities of existing analytical methodologies. However, functional and comparative genomic studies as well as proteomic approaches provide a wealth of knowledge in the way in which these lactic acid bacteria can use food proteins releasing bioactive peptides.

Molecular cloning of skin peptide precursor-encoding cDNAs from tibial gland secretion of the Giant Monkey Frog, Phyllomedusa bicolor (Hylidae, Anura)

The skins of phyllomedusine frogs have long been considered as being tremendously rich sources of bioactive peptides. Previous studies of both peptides and cloning of their precursor encoding cDNAs have relied upon methanolic skin extracts or the dissected skins of recently deceased specimens and have not considered the different glands in isolation. We therefore focused our attention on the tibial gland of the Giant Monkey Frog, Phyllomedusa bicolor and constructed a cDNA library from the skin secretion that was obtained via mechanical stimulation of this macrogland. Using shotgun cloning, four precursors encoding host-defense peptides were identified: two archetypal dermaseptins, a phyllokinin and a phylloseptin that is new for this species but has been recently described from the Waxy Monkey Leaf Frog, Phyllomedusa sauvagii. Our study is the first to report defensive peptides specifically isolated from anuran tibial glands, confirming the hypothesis that these glands also contribute to chemical defense. Moreover, the discovery of novel compounds for this otherwise very well characterized species suggests that this largely neglected gland might possess a different cocktail of secretions from glands elsewhere in the same animal. We will also discuss some evolutionary implications of our findings with respect to the adaptive plasticity of secretory glands.

Charaterization of bumarsin, a 3-hydroxy-3-methylglutaryl-coenzyme reductase inhibitor from Mesobuthus martensii Karsch venom

Scorpion venoms are rich sources of bioactive peptides and are widely known for their ion channel inhibiting properties. We have isolated, cloned and characterized a venom protein (Bumarsin) from the Chinese scorpion, Mesobuthus martensii Karsch. Bumarsin cDNA encodes a 8132 Da, 72 amino acid mature protein that most probably exists in its native form as a Cys-bridged homodimer. We have identified this novel protein to be an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase activity. 0.6 μM of Bumarsin inhibits 32% of the HMG-CoA reductase activity, in comparison to 10 μM simvastatin which only inhibits 35% of the activity. RT-PCR and SELDI-TOF mass spectrometric studies demonstrate that bumarsin regulates the expression of both genes and proteins involved in cholesterol homeostasis. Our results suggest that bumarsin may provide a model for the design of novel drugs that can be used to modulate cholesterol homeostasis.

A variant peptide of buffalo colostrum β-lactoglobulin inhibits angiotensin I-converting enzyme activity

β-lactoglobulin is a rich source of bioactive peptides. The LC-MS separated tryptic peptides of buffalo colostrum β-lactoglobulin (BLG-col) were computed based on MS–MS fragmentation for de novo sequencing. Among the selected peptides (P1–P8), a variant was detected with methionine at position 74 instead of glutamate. The sequences of two peptides were identical to hypocholesterolemic peptides whereas the remaining peptides were in accordance with buffalo milk β-lactoglobulin. Comparative sequence analysis of BLG-col to milk β-lactoglobulin was carried out using CLUSTALW2 and a molecular model for BLG-col was constructed (PMDB ID-PM0076812). The synthesized variant pentapeptide (IIAMK, m/z-576 Da) was found to inhibit angiotensin I-converting enzyme (ACE) with an IC50 of 498 ± 2 μM, which was rationalized through docking simulations using Molgrow virtual docker.

DADP: the database of anuran defense peptides

Anuran tissues, and especially skin, are a rich source of bioactive peptides and their precursors. We here present a manually curated database of antimicrobial and other defense peptides with a total of 2571 entries, most of them in the precursor form with demarcated signal peptide (SP), acidic proregion(s) and bioactive moiety(s) corresponding to 1923 non-identical bioactive sequences. Search functions on the corresponding web server facilitate the extraction of six distinct SP classes. The more conserved of these can be used for searching cDNA and UniProtKB databases for potential bioactive peptides, for creating PROSITE search patterns, and for phylogenetic analysis.

Angiotensin‐I Converting Enzyme Inhibitory and Antioxidant Activities of Egg Protein Hydrolysates Produced with Gastrointestinal and Nongastrointestinal Enzymes

Egg is a well-known rich source of bioactive peptides. In this study, egg protein (egg white and egg yolk proteins) hydrolysates were produced with gastrointestinal enzymes (pepsin and pancreatin) or nongastrointestinal enzymes (thermolysin and alcalase), and fractionated by ultrafiltration and cation exchange chromatography. Angiotensin-I converting enzyme (ACE) inhibitory and antioxidant activities, amino acid composition and molecular weight distribution were studied, and the physicochemical properties were related with the bioactivities. Our results showed that egg protein hydrolysates produced with non-GI enzymes (thermolysin and alcalase) showed significantly higher ACE inhibitory activity, whereas similar or even lower antioxidative activities, than those of hydrolysates produced with GI enzymes. ACE-inhibitory activity significantly correlated with the amino acid composition, especially the proportion of positively charged amino acid, whereas antioxidant activities correlated with the proportion of low molecular weight peptides under 500 Da. Understanding the relationship between the bioactivities and physicochemical properties of the hydrolysates/fractions is important to facilitate the development technologies for preparing fractions with improved bioactivities.

Three novel antimicrobial peptides from the skin of the Indian bronzed frog Hylarana temporalis (Anura: Ranidae)

Amphibian skin secretion is considered as a rich source of bioactive peptides. The present work describes the successful identification of three novel peptides named brevinin-1TEa, brevinin-2TEa and brevinin-2TEb present in the skin secretion of Indian bronzed frog Hylarana temporalis. The deduced open reading frame encoding the biosynthetic precursor of brevinin-1TEa consisted of 70 amino acid residues and brevinin-2TEa and brevinin-2TEb consisted of 71 and 72 amino acids, respectively. All the three peptides showed higher antimicrobial activity against Gram-negative than against Gram-positive bacteria. On the basis of the antibacterial and haemolytic activity, brevinin-2TEb is the most potent peptide reported in the present study. Further research on these peptides may provide potential clue towards newer drug development to combat various microbial diseases.

De novo sequencing of peptides from the parotid secretion of the cane toad, Bufo marinus (Rhinella marina)

Amphibian skin secretions are well known as a rich source of bioactive peptides. However, little is known about the presence or role of peptides in the highly toxic, parotid secretion of the cane toad or giant toad, Bufo marinus (Rhinella marina), though small molecule bufadienolides, which act as potent cardiotoxins, have been described. In the current study we used RP-HPLC, MALDI-TOF mass spectrometry and tandem mass spectrometry to analyze and determine the first sequences of peptides from the parotid secretion of B. marinus. We show that peptides in the range of 900–2500 Da are indeed present, however in extremely low abundance. Despite the low abundance, the sequences of 14 peptides were determined, several of which match fragments of larger cellular proteins, yet none share substantial homology with defensive or anti-microbial peptides reported from frog skin secretions. We conclude that peptides are present in the parotid glands of B. marinus only in very low quantities and that they are likely to be breakdown products of proteins involved in cell maintenance. Given these results, we conclude that peptides are unlikely to contribute directly to the high toxicity of the cane toad.

Bioactive peptides from food proteins: new opportunities and challenges

Food proteins such as milk and soy are a rich source of bioactive peptides. In the last decade, research into this area has intensified and new bioactive peptide sequences have been discovered with a range of apparent biological functions; for example, antihypertensive, antioxidant, and antimicrobial effects and opiate-like qualities have been reported. These peptides could therefore lead to the development of important functional food products and ingredients for the prevention and even treatment of chronic diseases such as cardiovascular disease and cancer. Peptides can be produced by fermentation with dairy starters for instance, and by enzymatic hydrolysis with pancreatic and microbial enzymes. Further purification is typically carried out by membrane filtration and/or chromatographic methods. The production of novel bioactive peptides and their incorporation into functional food products poses several technological challenges as well as regulatory and marketing issues. Proof of efficacy is of paramount importance; this should be verified by conducting appropriate tests in vivo in animals and in humans. In addition, tests for cytotoxicity and allergenicity must be conducted. Despite all of these hurdles, scientific evidence is increasingly demonstrating the health benefits of diet-based disease prevention, and therefore new developments in this area are likely to continue both at the research and the commercialisation level.

DNA in Amphibian and Reptile Venom Permits Access to Genomes without Specimen Sacrifice

Amphibian defensive skin secretions and reptile venoms are rich sources of bioactive peptides with potential pharmacological/pharmaceutical applications. As amphibian and reptile populations are in rapid global decline, our research group has been developing analytical methods that permit generation of robust molecular data from non-invasive skin secretion samples and venom samples. While previously we have demonstrated that parallel proteome and venom gland transcriptome analyses can be performed on such samples, here we report the presence of DNA that facilitates the more widely-used applications of gene sequencing, such as molecular phylogenetics, in a non-invasive manner that circumvents specimen sacrifice. From this “surrogate” tissue, we acquired partial 12S and 16S rRNA gene sequences that are presented for illustration purposes. Thus from a single sample of amphibian skin secretion and reptile venom, robust and complementary proteome, transcriptome and genome data can be generated for applications in diverse scientific disciplines.