Molecular Weight Peptides Research Articles

Liposome encapsulation of anionic and cationic whey peptides: Influence of peptide net charge on properties of the nanovesicles

Poor bioavailability of food-derived bioactive peptides impedes their application in functional foods. This study focuses on understanding the impact of net charge of whey peptides, separated by electrodialysis with ultrafiltration membrane (EDUF), on encapsulation efficiency (EE) and surface properties of the peptide-loaded liposomes. EDUF resulted in two fractions; anionic whey peptides (AWP) with a relative abundance of 30.4% anionic amino acid residues, and cationic whey peptides (CWP) with 20.39% cationic amino acid residues. Although free amino group of CWP was higher, average peptide length and molecular weight were similar in both fractions. AWP liposomes had slightly lower encapsulation efficiency than encapsulated CWP. Encapsulated CWP had larger mean particle diameter and higher polydispersity index. However, there was no apparent effect of peptide net charge on liposome surface charge (ζ-potential). FTIR spectra of the CWP- and AWP-loaded liposomes were similar and showed peptide interaction with the liposome phosphate groups. The peptide net charge did not appear to influence their distribution in different regions of the nanocapsules. The EE and physicochemical properties of the liposomes may be influenced by a combination of peptide net charge, homogeneity, and surface hydrophobicity. These findings are relevant to developing efficient liposomal systems for bioactive peptide delivery.

Improving nitrogen source utilization from defatted soybean meal for nisin production by enhancing proteolytic function of Lactococcus lactis F44

Nisin, one kind of natural antimicrobial peptide, is produced by certain Lactococcus lactis strains, which generally require expensive high-quality nitrogen sources due to limited ability of amino acids biosynthesis. Here we use defatted soybean meal (DSM) as sole nitrogen source to support L. lactis growth and nisin production. DSM medium composition and fermentation conditions were optimized using the methods of Plackett-Burman design and central composite design. The highest nisin production of 3879.58 IU/ml was obtained in DSM medium, which was 21.3% higher than that of commercial medium. To further increase the utilization ability of nitrogen sources, we enhanced the proteolytic function in L. lactis through rationally expressing the related enzymes, which were selected according to the compositions of amino acids and molecular weight of peptides in DSM medium. Significantly, an artificial proteolytic system consisting of a heterologous protease (NprB), an oligopeptides transporter subunit (OppA) and two peptidases (PepF and PepM) was introduced into L.lactis. The constructed strain BAFM was capable of achieving efficient biomass accumulation and nisin yield with 30% decreased amount of DSM hydrolysates, which further reduced the cost of nisin production. The strategy described here offers opportunities for low-cost L. lactis fermentation and large-scale nisin production in industry.

Dietary protein complexity modulates growth, protein utilisation and the expression of protein digestion-related genes in Senegalese sole larvae

Given its complex metamorphosis and digestive system ontogeny, Senegalese sole larvae capacity to digest and utilize dietary protein is likely to change throughout development. In the present study, we hypothesized that the manipulation of dietary protein complexity may affect Senegalese sole larvae capacity to digest, absorb and retain protein during metamorphosis, as well as the mRNA expression of genes encoding for the precursors of proteolytic enzymes of the digestive tract and the enterocyte peptide transporter PepT1, which may have further impact on somatic growth. Three diets were formulated using approximately the same practical ingredients, except for the main protein source. The Intact diet protein content was mostly based on intact plant protein where the target peptide molecular weight (MW) would be >70kDa. The PartH diet protein fraction was mostly based on a protein hydrolysate with a high content of 5–70kDa peptides. The HighH diet protein fraction was mostly based on a protein hydrolysate with a high content of 5kDa peptides. A growth trial was performed with larvae reared at 19°C under a co-feeding regime from mouth opening. The transcription of pga, tryp1c, ialp, ampn and pepT1 (encoding respectively for PepsinogenA, Trypsinogen1C, Intestinal alkaline phosphatase, Aminopeptidase N and for the enterocyte peptide transporter 1) was quantified by qPCR, during the metamorphosis climax (16DAH) and after the metamorphosis was completed (28DAH). An in vivo method of controlled tube-feeding was used to assess the effect on the larvae capacity to utilize polypeptides with different MW (1.0 and 7.2kDa) representing a typical peptide MW of each of the hydrolysates included in the diets. The PartH diet stimulated growth in metamorphosing larvae (16DAH), whereas the Intact diet stimulated growth after 36DAH. The Intact diet stimulated the larvae absorption capacity for 1.0kDa peptides at 16DAH, which may have contributed for enhanced growth in later stages. The PartH diet stimulated the transcription of tryp1c and pept1 at 28DAH, which seemed to reflect on increased post-larvae capacity to retain dietary 7.2kDa polypeptides. That may indicate a possible strategy to optimize the digestion and utilisation of the PartH dietary protein, though it did not reflect into increased growth. The Intact diet promoted the transcription of pepsinogenA, which may reflect a reduced gastrointestinal transit time, which could have enhanced the dietary nutrients assimilation, ultimately improving growth. The present results suggest that, whereas pre-metamorphic sole larvae utilize better dietary protein with a moderate degree of hydrolysis, post-metamorphic sole make a greater use of intact protein.

Effect of ultrasonic pretreatment on the antioxidant properties of porcine liver protein hydrolysates

SummaryIn this study, the effect of ultrasonic pretreatment on the antioxidant activity of porcine liver protein hydrolysates (PLPHs) was investigated. The results showed that the degree of hydrolysis (DH) and peptide contents of the PLPHs increased as the time of ultrasonication increased. The hydrolysate pretreated with ultrasonication for 60 s exhibited the highest DH and peptide contents. The hydrolysate pretreated with ultrasonication for 45 s exhibited the highest ferrous ion chelating ability and reducing power. The hydrolysate pretreated with ultrasonication for 30 s exhibited the highest 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging activity and the higher inhibitory activity in the linoleic acid autoxidation system. The molecular weight of peptides in the hydrolysates was less than 6.2 kDa. The results clearly demonstrated that ultrasonic pretreatment enhances the antioxidant activities of the PLPHs in a short period of time (15–30 s).

Antihypertensive peptides from animal products, marine organisms, and plants.

Bioactive peptides from food proteins exert beneficial effects on human health, such as angiotensin-converting enzyme (ACE) inhibition and antihypertensive activity. Several studies have reported that ACE-inhibitory peptides can come from animal products, marine organisms, and plants-derived by hydrolyzing enzymes such as pepsin, chymotrypsin, and trypsin-and microbial enzymes such as alcalase, thermolysin, flavourzyme, and proteinase K. Different ACE-inhibitory effects are closely related with different peptide sequences and molecular weights. Sequences of ACE-inhibitory peptides are composed of hydrophobic (proline) and aliphatic amino acids (isoleucine and leucine) at the N-terminus. As result of this review, we assume that low molecular weight peptides have a greater ACE inhibition because lower molecular weight peptides have a higher absorbency in the body. Therefore, the ACE-inhibitory effect is closely related with the degree of enzymatic hydrolysis and the composition of the peptide sequence.

Composition and protein profile analysis of rice protein ingredients

The objective of this study was to investigate the nutrient composition and protein profile of a range of rice protein ingredients containing 32–78% total protein. Rice protein ingredients had significantly (P<0.05) lower levels of calcium and total essential amino acids compared to selected dairy protein ingredients, i.e., skim milk powder, whey protein isolate and whey protein hydrolysate. Protein profiles of the ingredients were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and size exclusion-high pressure liquid chromatography (SE-HPLC). Since the dominant rice protein fraction (i.e., glutelin) is extensively aggregated and crosslinked through disulfide bonds, a strong reducing buffer was developed in order to solubilise the rice protein ingredients prior to analysis by SDS-PAGE. Intact rice protein ingredients (n=3) contained proteins with molecular weight (MW) ranging from ∼11 to >250kDa, while rice protein hydrolysates (n=4) were composed mainly of low MW peptides. In parallel, enriched protein fractions were extracted from defatted rice flour based on their solubility and characterised by SDS-PAGE to facilitate the identification of protein bands in the rice protein ingredients. The results of this study underpin the understanding, prediction and control of physicochemical functionality of rice protein ingredients.

Bioactive peptides with radical scavenging and cancer cell cytotoxic activities derived from Flathead (Platycephalus fuscus) by-products

Peptide fractions extracted from Flathead by-products were evaluated for in vitro free radical scavenging and cancer cell cytotoxic activities. The degree of hydrolysis (DH), presence of protease and molecular weight (MW) influenced the 2,2-diphenyl-1-pycryl-hydrazyl (DPPH) and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulphonic (ABTS) radical scavenging activities (RSA) of Flathead peptide fraction. Low MW peptides (<3 kDa), obtained from overnight incubation with added an exogenous protease, significantly inhibited free radicals and showed the highest RSA of 94.03 and 82.89 % against DPPH· and ABTS·+, respectively. The presence of bioactive peptides during H2O2 exposure increased viability of T4056 normal cells. Furthermore, peptide fractions <3 kDa inhibited the growth of HT-29 colon cancer cells up to 91.04 %, although the activity was found to be non-selective. Further purification revealed a novel peptide, Met-Gly-Pro-Pro-Gly-Leu-Ala-Gly-Ala-Pro-Gly-Glu-Ala-Gly-Arg, with RSA properties. These results indicated that peptides extracted from Flathead by-products have a potential to be used as natural antioxidants and/or chemo-protective agents.

New strategy for renal fibrosis: Targeting Smad3 proteins for ubiquitination and degradation

PurposeSmad3 is a critical signaling protein in renal fibrosis. Proteolysis targeting chimeric molecules (PROTACs) are small molecules designed to degrade target proteins via ubiquitination. They have three components: (1) a recognition motif for E3 ligase; (2) a linker; and (3) a ligand for the target protein. We aimed to design a new PROTAC to prevent renal fibrosis by targeting Smad3 proteins and using hydroxylated pentapeptide of hypoxia-inducible factor-1α as the recognition motif for von Hippel–Lindau (VHL) ubiquitin ligase (E3). MethodsComputer-aided drug design was used to find a specific ligand targeting Smad3. Surface plasmon resonance (SPR) was used to verify and optimize screening results. Synthesized PROTAC was validated by two-stage mass spectrometry. The PROTAC’s specificity for VHL (E3 ligase) was proved with two human renal carcinoma cell lines, 786-0 (VHL−) and ACHN (VHL+), and its anti-fibrosis effect was tested in renal fibrosis cell models. ResultsThirteen small molecular compounds (SMCs) were obtained from the Enamine library using GLIDE molecular docking program. SPR results showed that #8 SMC (EN300-72284) combined best with Smad3 (KD=4.547×10−5M). Mass spectrometry showed that synthesized PROTAC had the correct peptide molecular weights. Western blot showed Smad3 was degraded by PROTAC with whole-cell lysate of ACHN but not 786-0. Degradation, but not ubiquitination, of Smad3 was inhibited by proteasome inhibitor MG132. The upregulation of fibronectin and Collagen I induced by TGF-β1 in both renal fibroblast and mesangial cells were inhibited by PROTAC. ConclusionThe new PROTAC might prevent renal fibrosis by targeting Smad3 for ubiquitination and degradation.

Bioactive potency of epidermal mucus extracts from greasy grouper, Epinephelus tauvina (Forsskal, 1775)

Objective: To study the bio-potency of epidermal mucus from Epinephelus tauvina. Methods: Mucus was extracted with acidic, organic and aqueous solvents. Protein, carbohydrate, lipid, amino acid and fatty acid content of mucus extracts were quantified by UV-spectrophotometer, high performance liquid chromatography and gas chromatography- mass spectrometer, respectively. Antimicrobial activity was tested against five human and fish pathogens by using agar well diffusion method. The molecular weight of peptides was determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The haemolytic activity of extracts was tested against chick, goat, cow and human red blood cell. Results: Protein contributed with maximum of 26.25% in crude mucus. Arginine was recorded maximum of (133.9 nmol/mL) in crude mucus. 2,4,6-Decatrienoic acid and bis (a-chloroethyl) sulfone were confirmed in organic extract. The antimicrobial activity of acidic extract was significant. Among the human pathogens, maximum zone of inhibition ((26.0 ± 0.3) mm) was observed against Proteus mirabilis. Whereas, among fish pathogens maximum zone of inhibition ((25.0 ± 0.1) mm) was observed against Vibrio parahemolyticus. The activity of other two extracts was not remarkable. The molecular weight of peptides ranged from 115.5- 37.1 kDa in acidic extract was determined. Chicken and goat blood were found to be highly vulnerable to the lysis. Conclusions: The whole mucus could be a promising source with numerous bioactive- potency. Consequently, this preliminary information suggested that mucus is a source of novel antimicrobial agents for fish and human health related applications.

Encapsulation of bioactive whey peptides in soy lecithin-derived nanoliposomes: Influence of peptide molecular weight

Encapsulation of peptides can be used to enhance their stability, delivery and bioavailability. This study focused on the effect of the molecular weight range of whey peptides on their encapsulation within soy lecithin-derived nanoliposomes. Peptide molecular weight did not have a major impact on encapsulation efficiency or liposome size. However, it influenced peptide distribution amongst the surface, core, and bilayer regions of the liposomes, as determined by electrical charge (ζ-potential) and FTIR analysis. The liposome ζ-potential depended on peptide molecular weight, suggesting that the peptide charged groups were in different locations relative to the liposome surfaces. FTIR analysis indicated that the least hydrophobic peptide fractions interacted more strongly with choline on the liposome surfaces. The results suggested that the peptides were unequally distributed within the liposomes, even at the same encapsulation efficiency. These findings are important for designing delivery systems for commercial production of encapsulated peptides with improved functional attributes.

Comprehensive analysis of venom from the scorpion Centruroides tecomanus reveals compounds with antimicrobial, cytotoxic, and insecticidal activities

Centruroides tecomanus is a medically important scorpion of the state of Colima (Mexico). This communication reports the identification of venom components of this scorpion with biological activity over insects/crickets (Acheta domestica), crustaceans/fresh water shrimps (Cambarellus montezumae), and mammalians/mice (Mus musculus, strain CD1). It also describes the pharmacological effects on cell lines in culture (L5178Y cells, HeLa cells, HuTu cells and Jurkat E6-1 cells), as well as on several types of bacteria (see below). The soluble venom of this scorpion was fractionated by high-performance liquid chromatography (HPLC) and collected separately in twelve independent fractions collected over 60 min run (5 min time apart each other). The HPLC components of fraction VII were lethal to all three species used for assay. The IVth fraction had a toxic effect on freshwater shrimps. In this species, fractions VI, VII and VIII were all lethal. For crickets, fractions V and VI were toxic and fraction VII was lethal. In mouse, the lethal components were found in fraction VII, whereas fraction VIII was toxic, but not lethal, at the doses assayed. The molecular weight of peptides from the various group of fractions were identified by mass spectrometry determination. Components lethal to mice showed molecular weights from 7013 to 7487 Da. Two peptides were obtained in homogeneous form and shown to be lethal to the three species of animal used for assay. The soluble venom tested on L5178Y cell line survival was shown to be cytotoxic, at 10–100 μg/mL concentration, when compared to control murine splenocytes (p = 0.007). The soluble venom applied to Hela, Hutu and Jurkat cell lines did not show cytotoxic effects at these concentrations. On the contrary, it seems to have a proliferative effect. However the HPLC fractions I, III, VI and XII do have a cytotoxic effect on Jurkat E06-1 cells in culture at 200 μg/mL concentration. The antimicrobial activity of the venom fractions on Staphylococcus aureus (gram-positive), Escherichia coli, Pseudomonas aeruginosa y Salmonella spp (gram-negative) was measured, using the liquid inhibition growth system. The four strains of bacteria used were susceptible to fractions III and IV, affecting all four bacterial strains at concentrations below 5 μg/mL.

A novel approach to administration of peptides in women: Systemic absorption of a GnRH agonist via transvaginal ring delivery system

trans-Epithelial delivery of medication across the vagina has proven successful for administration of small, lipophilic molecules such as sex steroids. However, little information is available regarding the vaginal delivery of larger and more polar molecules that currently require parenteral administration because the vaginal epithelium is perceived as a barrier to absorption of larger molecular weight (MW) molecules. Six healthy women underwent administration of 18 or 36mg of leuprolide, a GnRH agonist and a larger MW peptide, via a novel ethylene vinyl acetate (EVA) ring transvaginal drug delivery system (TVDS). Serum levels rose within 8h following insertion: low dose at 310pg/ml and high dose at 1220pg/ml, i.e. levels typically following parenteral injections of leuprolide. GnRHa biological activity was validated by secretion of gonadotropins and sex steroids. These results demonstrate that the non-keratinized vaginal epithelium permits a rapid absorption of a biologically active peptide and that there is significant potential for a novel TVDS to deliver peptides and possibly other macromolecules therapeutically. Significance statementCurrent routes of administration of medications can include oral, subcutaneous, intravenous, intramuscular, transcutaneous, etc. Many of these approaches have limitations, including pain, poor tolerability, lack of adherence, and inadequate delivery. Peptides, in particular, cannot typically be given orally because they are broken down in the intestinal tract before they are absorbed. While the skin is an attractive way to deliver medications, its superb intrinsic barrier function often makes this route untenable at times. The vaginal epithelium, in contrast, is not keratinized and can allow absorption of other molecules. In this study, we demonstrate that a novel transvaginal drug delivery system (TVDS) is capable of delivering peptide therapeutics to women in a non-parenteral fashion as demonstrated by both blood levels and biologic effects of its delivery.

Identification of peptide molecular weight from rice bran protein hydrolysate with high antioxidant activity

The effects of the enzyme type (Alcalase, Flavourzyme and Neutrase) and hydrolysis time (2, 4 and 6 h) on properties of rice bran protein hydrolysate (RBPH) were studied. The enzyme type had significant effects on the protein yield and the properties of RBPH whereas the hydrolysis time was less influence. There were small differences in the total phenolic content and the ABTS radical scavenging activity between protease-hydrolyzed and unhydrolyzed rice bran protein, but enzymatic hydrolysis using Alcalase was the most effective providing hydrolysate with the highest protein yield and protein content. The optimal hydrolysis conditions was 2 h using an Alcalase-yielding protein content of 30.3%, a protein yield of 56.6%, TPC of 22.1 mg GAE/g, ABTS of 7.57 mg GAE/g and FRAP of 152 mM Fe2+/g. Fractionated peptides from this hydrolysate using anion exchange chromatography showed high antioxidant activity containing both positive and negative charge fractions with a low MW of 6 kDa. The RBPH using Alcalase could be a protein source and antioxidant in functional foods and beverages.

Controlled release of casein-derived peptides in the gastrointestinal environment by encapsulation in water-in-oil-in-water double emulsions

Dye-labeled peptides were produced by hydrolysis of azocasein and encapsulated in water-in-oil-in-water double emulsions. The effect of degree of hydrolysis (0%, 3.5%, or 7%) and oil phase composition (butter oil, linseed oil, or mineral oil) on the emulsion characteristics and peptide release kinetics during simulated gastrointestinal digestion was investigated. The double emulsions made from linseed oil and butter oil had smaller oil droplets, lower viscosity, and greater creaming stability than the double emulsion made from mineral oil did. The encapsulation efficiency was higher than 93%. The percentage of peptide release at the end of the gastric phase varied from 4% to 42%. Butter oil and linseed oil were attacked by the lipases during the intestinal phase of the digestion, and the peptide release increased progressively to more than 80%. The release of hydrolyzed azocasein was faster than the release of unhydrolyzed azocasein in both phases of digestion. Mineral oil was indigestible and strongly inhibited peptide release, which remained lower than 18%. The release behavior was strongly influenced by the composition as well as the hydrophobicity of the oil phase. Depending on peptide molecular weight, the kinetics of release can be controlled by adjusting oil phase composition.

Grass carp peptides hydrolysed by the combination of Alcalase and Neutrase: Angiotensin‐I converting enzyme (ACE) inhibitory activity, antioxidant activities and physicochemical profiles

SummaryIn this study, grass carp peptides were prepared by enzymatic hydrolysis of grass carp protein using the combination of Alcalase and Neutrase, and angiotensin‐I converting enzyme (ACE) inhibitory activity in vitro, antihypertensive activity in vivo, antioxidant activities, and physicochemical properties of peptides achieved from grass carp protein were characterised after ultrafiltration and desalted processes using mixed ion exchange resins. The purified peptides exhibited strong ACE inhibitory activity (IC50 = 105 μg mL−1), antihypertensive activity with the maximal drop for systolic blood pressure (SBP) of 43 mmHg at a dosage of 100 mg per kg body weight in spontaneously hypertensive rat (SHR), and antioxidant activities indicated by thiobarbituric acid‐reactive substance values in a liposome‐oxidising system, radical‐scavenging activity and chelation of metal ions (Fe2+). The molecular weight of peptides was &lt;1000 Da. Compared to grass carp protein, the peptides separated from enzymatic hydrolysates possessed similar amino acid compositions, but contained higher concentrations of essential amino acids. Moreover, the peptides exhibited excellent solubility at a wide range of pH values from 2 to 10, and lower apparent viscosity than the protein. The peptides separated from enzymatic hydrolysates might be used as a promising ingredient in antihypertensive functional foods and nutraceuticals.

Characterization of the Proteins Associated with Caulobacter crescentus Bacteriophage CbK Particles.

Bacteriophage genomes contain an abundance of genes that code for hypothetical proteins with either a conserved domain or no predicted function. The Caulobacter phage CbK has an unusual shape, designated morphotype B3 that consists of an elongated cylindrical head and a long flexible tail. To identify CbK proteins associated with the phage particle, intact phage particles were subjected to SDS-PAGE, and the resulting protein bands were digested with trypsin and analyzed using MALDI mass spectroscopy to provide peptide molecular weights. These peptide molecular weights were then compared with the peptides that would be generated from the predicted amino acid sequences that are coded by the CbK genome, and the comparison of the actual and predicted peptide masses resulted in the identification of single genes that could code for the set of peptides derived from each of the 20 phage proteins. We also found that CsCl density gradient centrifugation resulted in the separation of empty phage heads, phage heads containing material organized in a spiral, isolated phage tails, and other particulate material from the intact phage particles. This additional material proved to be a good source of additional phage proteins, and preliminary results suggest that it may include a CbK DNA replication complex.

Inhibition of SERPINe1 reduces rhabdoviral infections in zebrafish.

While exploring the molecular mechanisms behind the fin hemorrhages that follow zebrafish (Danio rerio) early infection with viral haemorrhagic septicemia virus (VHSV), we discovered that most serpin (serine protease inhibitor) gene transcripts were upregulated, except those of serpine1. Surprisingly, only SERPINe1-derived 14-mer peptide and low molecular weight drugs targeting SERPINe1 (i.e. tannic acid, EGCG, tiplaxtinin) inhibited in vitro infections not only of VHSV, but also of other fish rhabdoviruses such as infectious hematopoietic necrosis virus (IHNV) and spring viremia carp virus (SVCV). While the mechanisms that inhibited rhabdoviral infections remain speculative, these and other results suggested that SERPINEe1-derived peptide specifically targeted viral infectivity rather than virions. Practical applications might be developed from these studies since preliminary evidences showed that tannic acid could be used to reduce VHSV-caused mortalities. These studies are an example of how the identification of host genes targeted by viral infections using microarrays might facilitate the identification of novel prevention drugs in aquaculture and illuminate viral infection mechanisms.

Clinical predictive circulating peptides in rectal cancer patients treated with neoadjuvant chemoradiotherapy.

Preoperative chemoradiotherapy is worldwide accepted as a standard treatment for locally advanced rectal cancer. Current standard of treatment includes administration of ionizing radiation for 45-50.4 Gy in 25-28 fractions associated with 5-fluorouracil administration during radiation therapy. Unfortunately, 40% of patients have a poor or absent response and novel predictive biomarkers are demanding. For the first time, we apply a novel peptidomic methodology and analysis in rectal cancer patients treated with preoperative chemoradiotherapy. Circulating peptides (Molecular Weight <3 kDa) have been harvested from patients' plasma (n = 33) using nanoporous silica chip and analyzed by Matrix-Assisted Laser Desorption/Ionization-Time of Flight mass spectrometer. Peptides fingerprint has been compared between responders and non-responders. Random Forest classification selected three peptides at m/z 1082.552, 1098.537, and 1104.538 that were able to correctly discriminate between responders (n = 16) and non-responders (n = 17) before therapy (T0) providing an overall accuracy of 86% and an area under the receiver operating characteristic (ROC) curve of 0.92. In conclusion, the nanoporous silica chip coupled to mass spectrometry method was found to be a realistic method for plasma-based peptide analysis and we provide the first list of predictive circulating biomarker peptides in rectal cancer patients underwent preoperative chemoradiotherapy.

Antioxidant peptides from corn gluten meal: Orthogonal design evaluation

Protamex catalyzed corn gluten meal (CGM) hydrolysis peptides (CHP) were prepared. Orthogonal design L16 (45) was used to optimize processing variables of CGM concentration, CGM heat pretreatment (121°C) time, and enzymolysis pH, temperature, and time. Degree of hydrolysis (DH), undigested residue ratio, molecular weight (MW) distribution and DPPH radical inhibition were selected as analysis indicators. Optimum variables were CGM concentration of 18%, heat pretreatment time of 40min, and enzymolysis pH, temperature and time of 7.5, 55°C and 24h, respectively. Verification test showed that CHP IC50 for scavenging hydroxyl radical was the best and then followed by reducing power. Oligopeptides improved after hydrolysis at the expense of di- and tripeptides, suggesting formation of soluble aggregates from low MW peptides. The increase in the DH, oligopeptides, Alanyl-Tyrosine, and antioxidant free amino acids coincided with the improvement in the antioxidant activity of CHP.

Protein hydrolysate from tilapia frame: antioxidant and angiotensin I converting enzyme inhibitor properties

SummaryThe effect of varying the aminopeptidase concentration and hydrolysis time in the production of a protein hydrolysate from tilapia frame (TFPH) was evaluated in terms of the obtained antioxidant and angiotensin I converting enzyme (ACE) inhibitor activities. Minced tilapia frame was subjected to hydrolysis using three concentrations Flavourzyme® 1000 L [Brenntag Ingredients (Thailand) Company Limited (Public), Bangkok, Thailand] [0%, 1% and 2% (w/w)] and two hydrolysis times (0 and 1 h). The enzyme concentration and hydrolysis time both significantly affected the antioxidant and ACE inhibitor properties. The use of 2% (w/w) Flavourzyme® 1000 L for 1 h yielded the highest levels of 2,2‐diphenyl‐1‐picrylhydrazil free radical scavenging (90.4%), metal chelating (91.8%), thiobarbituric acid activity ratio (81.9%), and ACE inhibition (83.8%). In addition, this TFPH contained a higher net amount of amino acids and a larger peptide molecular weight distribution compared to the unhydrolysed tilapia frame supernatant. Thus, TFPH may be a suitable supplement to improve the functionality of food products.