Low Molecular Weight Peptide Fractions Research Articles

Regulation mechanisms of sea cucumber peptides against scopolamine-induced memory disorder and novel memory-improving peptides identification

Memory impairment affects cognition and information processing, and attention, leading to a decline in life quality of patients. Previous studies have shown the memory-improving effects of sea cucumber peptides. This study further explored the memory-improving mechanisms of sea cucumber peptides using scopolamine-induced memory-impaired mice and identified novel memory-improving peptides within low molecular weight peptide fractions. The sea cucumber peptides were categorized into three groups based on their molecular weights: SCP-L (molecular weight greater than 10 kDa), SCP-M (weight between 3 kDa and 10 kDa), and SCP-S (molecular weight less than 3 kDa). The results showed that SCP-S improved behavioral performance by regulating cholinergic system disorder and reducing oxidative stress levels, distinguishing itself from SCP-M and SCP-L. Further, SCP-S was found to exhibit a well ability in alleviating the degree of neuroinflammation dependent on microglia and promoting synaptic plasticity. Additionally, a novel memory-improving peptide Ser-Phe-Gly-Asp-Ile (SFGDI) was identified by EASY-nano-LC/MS/MS after simulated digestion-absorption coupling of in silico technologies from SCP-S. SFGDI protected against oxidative stress and regulated cholinergic system in scopolamine-induced PC12 cells. These findings suggest that SCP-S and SFGDI might be considered as potential memory-improving food for people suffering from memory disorders.

Low Molecular Weight Peptide Fraction from Poultry Byproduct Hydrolysate Features Dual ACE-1 and DPP4 Inhibition

Low Molecular Weight Peptide Fraction from Poultry Byproduct Hydrolysate Features Dual ACE-1 and DPP4 Inhibition

Application of assisted extraction technologies to optimize the extraction of biologically active substances from plant materials

There is an increased interest in obtaining amaranth grain extracts enriched with biologically active substances by deep processing of raw materials with a further prospect of their use as part of specialized multi-purpose food products. The aim of this work was to evaluate the effectiveness of membrane filtration for the extraction of biologically active substances from amaranth grains. Amaranth grain extract was obtained by enzymatic hydrolysis using a proteolytic enzyme followed by membrane treatment. the developed approach made it possible to obtain an extract from amaranth grains - a source of biologically active peptides, 20-hydroxyecdysone and polyphenols (including saponins). In total, triterpene saponins were concentrated in the extract by 8 times, and the phytoecdysteroid 20-hydroxyecdysone was more than 30 times concentrated. The high content of low molecular weight peptide fractions (more than 80%) in the composition of the extract makes it promising to evaluate its antihypertensive and antidiabetic properties in vivo. The presence of 20-hydroxyecdysone in the extract, an adaptogen with a proven effect, opens up the possibility of its use as a functional food ingredient in specialized food products, including for athletes.

A peptide fraction from hardened common beans (Phaseolus vulgaris) induces endothelium-dependent antihypertensive and renal effects in rats

Beans reached the research spotlight as a source of bioactive compounds capable of modulating different functions. Recently, we reported antioxidant and oxidonitrergic effect of a low molecular weight peptide fraction (<3 kDa) from hardened bean (Phaseolus vulgaris) in vitro and ex vivo, which necessitate further in vivo assessments. This work aimed to evaluate the hypotensive effect and the involved physiological mechanisms of the hardened common bean peptide (Phaseolus vulgaris) in normotensive (Wistar) and hypertensive (SHR) animals. Bean flour was combined with a solution containing acetonitrile, water and formic acid (25: 24: 1). Protein extract (PV3) was fractioned (3 kDa membrane). We assessed PV3 effects on renal function and hemodynamics of wistar (WT–normotensive) and spontaneously hypertensive rats (SHR) and measured systemic arterial pressure and flow in aortic and renal beds. The potential endothelial and oxidonitrergic involvements were tested in isolated renal artery rings. As results, we found that PV3: I) decreased food consumption in SHR, increased water intake and urinary volume in WT, increased glomerular filtration rate in WT and SHR, caused natriuresis in SHR; II) caused NO- and endothelium-dependent vasorelaxation in renal artery rings; III) reduced arterial pressure and resistance in aortic and renal vascular beds; IV) caused antihypertensive effects in a dose-dependent manner. Current findings support PV3 as a source of bioactive peptides and raise the potential of composing nutraceutical formulations to treat renal and cardiovascular diseases.

Identification, molecular docking, and kinetic studies of six novel angiotensin-I-converting enzyme (ACE) inhibitory peptides derived from Kenaf (Hibiscus cannabinus L.) seed

Kenaf (Hibiscus cannabinus L.) seed is a valuable protein source that could be used to prepare protein hydrolysates with antihypertensive properties. However, the potential of using kenaf seeds for health food and pharmaceutical applications has not been fully exploited. Thus, the aim of this study was to identify and characterise the Angiotensin-I-Converting Enzyme (ACE) inhibitory peptides derived from the optimized hydrolysis conditions of kenaf seed protein hydrolysates (KSPH). The optimum hydrolysis conditions determined by response surface methodology (RSM) were as follows: temperature 65 °C, pH 6.5, hydrolysis time 2.25 h, and enzyme/substrate (E/S) ratio of 0.03 (w/w). Under these conditions, the degree of hydrolysis (DH) was 55.28 % and ACE inhibitory activity was 75.51 %. Also, the low molecular weight peptide fractions, <2 kilodalton (kDa) and 2–5 kDa showed the highest ACE-inhibitory activity (82.27 % and 83.69 %, respectively). The 2–5 kDa fraction by Quadrupole-Time-of-Flight Liquid Chromatography-Mass Spectrometry (QTOF LC − MS) revealed the abundance of six peptides, LYWSYLYN, ALFYWVS, LLLHAL, AKSCVVFP, INPPSTTN, and WTIPTPS. Kinetic studies showed that peptide LYWSYLYN possessed the highest Michaelis constant (Km), maximum velocity (Vmax) values and the lowest inhibitor constant (Ki) values, suggesting of its superior ACE inhibitory activity compared to other peptides.

Behavioral effects of a low molecular weight peptide fraction from Phaseolus vulgaris in rats.

Seminal studies stated that bean proteins are efficient neuronal tracers with affinity for brain tissue. A low molecular weight peptide fraction (<3kDa) from Phaseolus vulgaris (PV3) was previously reported to be antioxidant, non-cytotoxic, and capable of reducing reactive oxygen species and increasing nitric oxide in cells. We evaluated the effects of PV3 (5, 50, 100, 500, and 5000 µg/kg) on behavior and the molecular routes potentially involved. Acute and chronic PV3 treatments were performed before testing Wistar rats: i) in the elevated plus-maze (EPM) to assess the anxiolytic-like effect; ii) in the open field (OF) to evaluate locomotion and exploration; and iii) for depression-like behavior in forced swimming (FS). Catecholaminergic involvement was tested using the tyrosine hydroxylases (TH) enzyme inhibitor, α-methyl-DL-tyrosine (AMPT). Brain areas of chronically treated groups were dissected to assess: i) lipid peroxidation (LPO); ii) carbonylated proteins (CP); iii) superoxide dismutase (SOD) and catalase (CAT) enzymatic activities. Neuronal nitric oxide synthases (nNOS) and argininosuccinate synthase (ASS) protein expression was evaluated by western blotting. Acute treatment with PV3 increased the frequency and time spent in the EPM open arms, suggesting anxiolysis. PV3 increased crossing episodes in the OF. These PV3 effects on anxiety and locomotion were absent in the chronically treated group. Acute and chronic PV3 treatments reduced the immobility time in the FS test, suggesting an antidepressant effect. TH inhibition by AMPT reverted acute PV3 effects. PV3 decreased LPO and CP levels and SOD and CAT activities, whereas nNOS and ASS were reduced in few brain areas. In conclusion, PV3 displayed central antioxidant actions that are concomitant to catecholaminergic-dependent anxiolytic and antidepressant effects.

Production and Fractionation of Rocky Shore Crab (Grapsus albacarinous) Protein Hydrolysate by Ultrafiltration Membrane: Assessment of Antioxidant and Cytotoxic Activities

ABSTRACT Bioactive peptides from marine protein sources hold tremendous promise as potent antioxidant agents with plausible anticancer activity. Herein, the antioxidant activities of crab protein hydrolysate and its ultrafiltration fractions at different molecular weights (>30 kDa,10–30 kDa,3–10 kD and<3 kDa) using various methods (DPPH, ABTS and FRAP assay) were investigated carefully. The results showed that although all peptide fractions from the crab hydrolysate showed some activity, the low molecular weight fractions (3–10 kDa and <3 kDa) generated the highest antioxidant activity, with a high content of hydrophobic amino acids (48.87% for 3–10 and 46.26% for <3 kDa). Interestingly, both low molecular weight peptide fractions showed a remarkable cytotoxic effect against the MCF-7 cells, while the 3–10 kDa peptide fraction proved to be more effective. Phase-contrast microscopy of treated MCF7 cells with the 3–10 peptide fraction confirmed various morphological alterations and cell damages. Overall, the study suggested that the low molecular weight peptide fractions of rocky shore crab Grapsus albolineatus hydrolysate could be considered as a natural antioxidant candidate in the prevention of cancer by reducing free radicals production, as well as an anticancer agent in cancer treatment by cytotoxic effect on cancer cells.

Effect of Molecular Weight of Tilapia (Oreochromis Niloticus) Skin Collagen Peptide Fractions on Zinc-Chelating Capacity and Bioaccessibility of the Zinc-Peptide Fractions Complexes in Vitro Digestion

To investigate the effect of the molecular weight of tilapia skin collagen peptide fractions on their zinc chelation capacity and the bioaccessibility of their zinc complexes, we evaluated the zinc-chelating ability of different molecular weight peptide, the solubility, and the stability of the complexes during simulated in vitro digestion. Low molecular weight peptide (P1) exhibited a higher zinc-chelating ability, which can be attributed to the variety of metal chelate amino acid residues. The highest solubility and the lowest release of zinc during peptic digestion for the P1-zinc complex and the zinc binding to P1 were retained at approximately 50% after peptic-pancreatic digestion. Fourier transform infrared spectroscopy indicated the primary involvement of the N-H group in all peptide-zinc complexes. This finding suggests that low molecular weight peptidefraction with strong zinc chelation ability can be used as delivery agents to improve zinc bioaccessibility.

Peptide profile and free radical scavenging activity of the low molecular weight peptide fraction from whole body extracts of &lt;i&gt;Tympanotonus fuscatus&lt;/i&gt; var radula (Linnaeus) and &lt;i&gt;Pachymelania aurita&lt;/i&gt; (Muller)

Low molecular weight peptides are among the most active bioactive components that have been isolated from marine molluscs. Currently, peptides isolated from molluscs as well as their synthetic structural analogues are in clinical trials as anticancer compounds and have been approved for use in pain management. These Bioactive peptides have also been demonstrated to exhibit antioxidant activities. This study aimed at isolating and profiling the low molecular weight peptide fractions from extracts of two common marine molluscs; P. aurita and T. fuscatus obtained from the Niger-Delta region of Nigeria. This study also investigated the free radical scavenging activity of the isolated fraction. Fourier Transform Infrared Spectroscopy analysis was carried out to determine the chemical entities and common functional groups found in the extracts. The Low molecular weight peptides were isolated using Molecular sieve chromatography, while the peptide profiles were established using SDS-PAGE and Thin Layer Chromatography (TLC). The free radical scavenging potential of the peptides was also assessed qualitatively using TLC, with DPPH as stain. The results show the presence of several low molecular weight peptides in the extracts of both P. aurita and T. fuscatus. Yellow spot on a purple background, indicating antioxidant activity was observed in the TLC plates sprayed before the chromatographic run. This activity was lost on further separation, indicating a synergistic effect. Further studies to effectively separate these fractions into individual peptides, investigate the synergistic effect observed as well as further explorations of possible bioactivity of these peptides is required.© 2019 International Formulae Group. All rights reserved.Keywords: Tympanotonus fuscatus var radula, Pachymelania aurita, peptides, FT-IR, free- radical scavenging

Peptides from chicken processing by-product inhibit DPP-IV and promote cellular glucose uptake: potential ingredients for T2D management.

Inhibition of dipeptidyl peptidase IV (DPP-IV) and stimulation of muscle glucose uptake are two of the key strategies for management of type-2-diabetes (T2D). In the present study, four protein hydrolysates generated by enzymatic hydrolysis of chicken by-product, i.e., mechanical chicken deboning residue, were evaluated for their DPP-IV inhibitory activity as well as their effect on glucose uptake by skeletal muscle cells. The DPP-IV inhibitory assay was performed at two concentrations (1000 μg mL-1 and 10 μg mL-1) for the crude chicken protein hydrolysates. The hydrolysate with the highest DPP-IV inhibition was selected for preparative-scale fractionation using size-exclusion chromatography (SEC). The SEC fractions were tested for DPP-IV inhibitory activity as well as their effect on glucose uptake and metabolic activity of skeletal muscle cells. The muscle cells were treated with the SEC fractions and glucose uptake was measured based on luminescence detection of 2-deoxyglucose-6-phosphate (2DG6P). A fraction with peptides in the lower molecular weight range was shown to promote glucose uptake and to inhibit DPP-IV. Further chromatographic fractionation followed by inhibition assaying of the most potent SEC fraction led to isolation of five refined peptide fractions with more than 80% DPP-IV inhibition, which were subsequently analyzed with LC-HRMS/MS. This led to identification of 14 peptides as potential DPP-IV inhibitors from protein hydrolysates of mechanical chicken deboning residue.

Inhibitory properties of bambara groundnut protein hydrolysate and peptide fractions against angiotensin-converting enzymes, renin and free radicals.

An increased rate of high blood pressure has led to critical human hypertensive conditions in most nations. In the present study, bambara protein hydrolysates (BPHs) obtained using three different proteases (alcalase, trypsin and pepsin) and their peptide fractions (molecular weight: 10, 5, 3 and 1 kDa) were investigated for antihypertensive and antioxidant activities. Alcalase hydrolysate contained the highest amount of low molecular weight (LMW) peptides compared to pepsin and trypsin hydrolysates. LMW peptides fractions (<1 kDa) exhibited the highest inhibitory activity against angiotensin-converting enzyme (ACE) for all the enzymes hydrolysates. For renin inhibition, alcalase hydrolysate showed the highest inhibition at 59% compared to other hydrolysates and their corresponding membrane fractions. The antioxidant power of bambara protein hydrolysates and peptide fractions was evaluated through the inhibition of linoleic acid peroxidation and ABTS scavenging activity. Among the hydrolysates, alcalase exhibited the highest inhibition of linoleic acid oxidation. Furthermore, all BPHs were able to scavenge ABTS•+ to a three-fold greater extent compared to the isolate. BPH and LMW peptide fractions could potentially serve as useful ingredients in the formulation of functional foods and nutraceuticals against high blood pressure and oxidative stress. © 2016 Society of Chemical Industry.

Proteomic Analysis of the Low Molecular Weight Peptide Fraction in Serum of Obese Zucker Rat

Obesity is a major risk factor for the development of cardiovascular disease, diabetes and certain types of cancer. Analysis of serum components represents a minimally invasive method for detecting biomarkers of obesity‐associated risk. Analysis of potential serum biomarkers is either focused on the levels of serum proteins or on the abundance of low molecular weight peptides that constitute the serum peptidome. In this study, we used quantitative tandem mass spectrometry to measure differences in the serum peptidome of obese Zucker rats. Lean and obese female Zucker rats (n=16) were assigned to AIN‐93‐G diet for 8 weeks, serum samples were collected and kept at ‐20 C until analysis. As expected, obese rats gained significantly (P&lt;0.001) more weight than lean rats. Using Tandem Mass Tags (TMTs), we were able to identify and quantify a set of peptides that were elevated in the serum of obese Zucker rats. Peptides derived from apoE and the coordinately regulated apoA1, apoCIII,and apoA1 were all significantly higher in the obese rats suggesting an increase in lipoprotein metabolism. In addition, we found that fibrinogen‐derived peptides were higher in obese rats indicating enhanced inflammation. Together our results suggest that obesity induced metabolic and inflammatory changes are reflected in the serum peptidome. Supported by R01GM106024 to AJT and ABI to RH.

Production and characterization of angiotensin converting enzyme (ACE) inhibitory peptides from apricot (Prunus armeniaca L.) kernel protein hydrolysate

Six different proteases (Flavourzyme®, Neutrase®, Protamex®, Alcalase® 2.4L, Proleather® FG-F, and papain) were employed to hydrolyze apricot kernel protein (AKP). Alcalase® is an inexpensive and non-specific protease that has been shown to be useful for the generation of bioactive peptides from AKP. Alcalase® 2.4L was selected for further study on enzymatic preparation of ACE inhibitory peptide from AKP. After 60-min hydrolysis, the highest ACE inhibition was 82 ± 0.14%. Results of molecular weight distribution revealed that most of ACE inhibition activity was probably attributed to low-molecular weight peptide fraction ranging from 200 to 900 Da. Ultrafiltration on membranes with several molecular weight cutoffs (MWCFs) demonstrated that most of the ACE inhibitory activity was due to peptides with a less than 1,000 Da molecular weight: the IC50 value of the 1-kDa ultrafiltrate was 0.15 ± 0.007 mg mL−1, while it was 0.378 ± 0.015 mg mL−1 before ultrafiltration. Additionally, further separation and purification of the ACE inhibitory peptides were carried out using gel filtration and C18 RP-HPLC. The result of research can be used to optimize AKP enzymatic hydrolysis for producing ACE inhibitory peptides which could be used for food industry and nutraceuticals.

Release of Protein-Bound N-ε -(γ -glutamyl)-Lysine during Simulated Gastrointestinal Digestion

&lt;I&gt;N&lt;/I&gt;-&amp;epsilon; -(&amp;gamma; -glutamyl)-lysine is a crosslinking amino acid formed in food mainly during treatment with microbial transglutaminase (mTG). The purpose of this study was to investigate to which amount isopeptides are detectable in a low-molecular weight peptide fraction after simulated gastrointestinal digestion. Casein, which had been enriched with &lt;I&gt;N&lt;/I&gt;-&amp;epsilon; -(&amp;gamma;-glutamyl)-lysine by mTG to different extents, was subjected to simulated gastrointestinal digestion and the resulting peptide mixture fractionated into a low- and a high molecular weight fraction (below or above 200–500 Da, respectively) using semipreparative gel permeation chromatography. &lt;I&gt;N&lt;/I&gt;-&amp;epsilon; -(&amp;gamma;-glutamyl)-lysine was analysed in these fractions by RP-HPLC after enzymatic hydrolysis and derivatisation with phenyl isothiocyanate. &lt;I&gt;N&lt;/I&gt;-&amp;epsilon; -(&amp;gamma;-glutamyl)-lysine was found nearly exclusively in the high-molecular weight fraction, indicating that dietary &lt;I&gt;N&lt;/I&gt;-&amp;epsilon; -(&amp;gamma;-glutamyl)-lysine present in mTG-modified food proteins is not available for absorption in the intestine.

FORMATION OF TASTE AND ODOR COMPOUNDS DURING PREPARATION OF DOUCHIBA, A CHINESE TRADITIONAL SOY-FERMENTED APPETIZER

Douchiba (DCB), a Chinese traditional soy-fermented appetizer, is abundantly produced and widely consumed in Guizhou province of southwest China. In this study, an analysis of free amino acid (FAA) profiles, low-molecular weight peptide fractions (LMWPFs), hydrophobic bitter peptide fractions (HBPFs) and volatile compounds was conducted to understand the changes in taste and odor compounds of DCB during five consecutive manufacturing stages: steamed soybean (SS), 5-day incubated Koji (Koji), 6-month fermented Douchi, semifinished Douchiba (sm-DCB) and 6-month ripened finished Douchiba (DCB). The total free amino acids (TFAAs) increased significantly from SS to DCB by about 11 times and amounted to 20.1% of the crude protein. Arg, Glu, Phe, Leu and Lys were the most abundant FAA at the end of ripening, and were 64.6% of TFAA. The most abundant taste active FAA classes were the bitter FAA, representing eight- and threefold increases over sweet and MSG-like FAA, respectively. The final values of all bitter and monosodium glutamate-like (MSG-like) FAA at DCB stage were significantly higher than their respective thresholds. The of oligopeptides (500∼1000 Da) accounted for 13.8 and 2.5% of LMWPF and HBPF, respectively. However, the taste of DCB was predominated by saltiness, followed by moderate umami taste and slight bitterness, likely as a result of the and interaction among different taste components. A total of 122 volatile compounds were identified, including alcohols, acids, esters, aldehydes, ketones, phenols, sulfur-containing compounds, heterocyclic compounds, alkines, benzenes and spice aromatics. The subtle aroma of the finished DCB seemed to depend not only on particular key compounds but also on a critical balance or a weighted concentration ratio of 60 compounds. These volatile compounds, mainly derived from lipid oxidation, amino acid degradation, carbohydrate fermentation, Maillard reaction and Strecker degradation during the microbial metabolism, enzymatic catalysis and spontaneous reactions.

Serum proteases alter the antigenicity of peptides presented by class I major histocompatibility complex molecules.

Any effect of serum on the antigenicity of peptides is potentially relevant to their use as immunogens in vivo. Here we demonstrate that serum contains distinct proteases that can increase or decrease the antigenicity of peptides. By using a functional assay, we show that a serum component other than beta 2-microglobulin enhances the presentation of ovalbumin peptides produced by cyanogen bromide cleavage. Three features of this serum activity implicate proteolysis: it is temperature dependent, it results in increased antigenicity in a low molecular weight peptide fraction, and it is inhibited by the protease inhibitor leupeptin. Conversely, presentation of the synthetic peptide OVA-(257-264) is inhibited by serum. This inhibition is unaffected by leupeptin but is blocked by bestatin, a protease inhibitor with distinct substrate specificities. Implications for peptide-based vaccine design and immunotherapy are discussed.

Inhibition of progesterone secretion in cultured human granulosa cells by a low molecular weight fraction of human follicular fluid.

Previous studies demonstrated that a low molecular weight peptide fraction (G10-3) from human follicular fluid (FFl) could inhibit steroidogenesis by rat granulosa cells in vitro. In the present study this FFl fraction was tested upon human granulosa cells. The G10-3 fraction (less than 1000 mol wt) was obtained by sequential gel filtration on Sephadex G50 and G10 of a steroid-free extract of a pool of human FFl collected from various-sized follicles at different stages of the menstrual cycle. Human granulosa cells were obtained from large, healthy follicles in the mid- to late follicular phase of eight patients, and cultured for 4-6 days in the absence or presence of G10-3. In all cases G10-3 produced a dose-dependent inhibition of basal progesterone secretion and, when tested, also of FSH-stimulated progesterone secretion. Inhibition of progesterone secretion appeared to be greater in cells obtained from less mature follicles as compared to cells obtained from follicles that were periovulatory. The results suggest the presence of a low molecular weight luteinizing inhibitor in human FFl.

Modifications of some peptic alfalfa leaf protein peptides as a result of plastein reaction with immobilized α-chymotrypsin

Changes in peptides and their amino-acid composition that take place during the plastein reaction carried out with immobilizedα-chymotrypsin as a catalyst and with the low-molecular weight peptide fraction of alfalfa (Medicago sativa) leaf protein hydrolyzate as substrate were studied. By thin-layer fingerprint chromatography the substrate and the plastein reaction product exhibited five and six peptide species, respectively. The analysis of their amino-acid composition indicated that the substrate peptides in two cases gave rise to plastein peptides by slight apparent compositional changes, in the other cases instead they underwent more pronounced modifications.