Bioactive peptides and proteins

WITHDRAWN: Bioactive peptides derived from meat proteins

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Possible role of milk-derived bioactive peptides in the treatment and prevention of metabolic syndrome

The growing prevalence of metabolic syndrome as well as its impact on public health has garnered increased attention in recent years. As a result, metabolic syndrome is now considered one of the world's leading public health problems. Bioactive peptides deriving from milk proteins may play an important role in the prevention and treatment of metabolic syndrome and its complications via several mechanisms, such as the satiety response, the regulation of insulinemia levels and blood pressure, the uptake of free radicals, and alteration of the lipid profile. These peptides can be incorporated into functional foods or administered via nutraceuticals to decrease the risk of obesity, atherogenesis, arterial hypertension, and type 2 diabetes. Recent findings have generated considerable scientific and commercial interest in milk-derived bioactive peptides, leading to numerous publications on the effectiveness of these substances. This review summarizes the current knowledge on bioactive peptides derived from milk proteins and examines the potential value of these peptides in the treatment and prevention of metabolic syndrome and its complications.

Lactoferrin inhibits Porphyromonas gingivalis proteinases and has sustained biofilm inhibitory activity

Porphyromonas gingivalis is a bacterial pathogen associated with chronic periodontitis that results in destruction of the tooth's supporting tissues. The major virulence determinants of P. gingivalis are its cell surface Arg- and Lys-specific cysteine proteinases, RgpA/B and Kgp. Lactoferrin (LF), an 80-kDa iron-binding glycoprotein found in saliva and gingival crevicular fluid, is believed to play an important role in innate immunity. In this study, bovine milk LF displayed proteinase inhibitory activity against P. gingivalis whole cells, significantly inhibiting both Arg- and Lys-specific proteolytic activities. LF inhibited the Arg-specific activity of purified RgpB, which lacks adhesin domains, and also inhibited the same activity of the RgpA/Kgp proteinase-adhesin complexes in a time-dependent manner, with a first-order inactivation rate constant (k(inact)) of 0.023 min(-1) and an inhibitor affinity constant (K(I)) of 5.02 μM. LF inhibited P. gingivalis biofilm formation by >80% at concentrations above 0.625 μM. LF was relatively resistant to hydrolysis by P. gingivalis cells but was cleaved into two major polypeptides (53 and 33 kDa) at R(284) to S(285), as determined by in-source decay mass spectrometry; however, these polypeptides remained associated with each other and retained inhibitory activity. The biofilm inhibitory activity of LF against P. gingivalis was not attributed to direct antibacterial activity, as LF displayed little growth inhibitory activity against planktonic cells. As the known RgpA/B and Kgp inhibitor N-α-p-tosyl-l-lysine chloromethylketone also inhibited P. gingivalis biofilm formation, the antibiofilm effect of LF may at least in part be attributable to its antiproteinase activity.

A review of fish-derived antioxidant and antimicrobial peptides: their production, assessment, and applications

Fishes are rich sources of structurally diverse bioactive compounds. In recent years, much attention has been paid to the existence of peptides with biological activities and proteins derived from foods that might have beneficial effects for humans. Antioxidant and antimicrobial peptides isolated from fish sources may be used as functional ingredients in food formulations to promote consumer health and improve the shelf life of food products. This paper presents an overview of the antioxidant and antimicrobial peptides derived from various fishes. In addition, we discuss the extraction of fish proteins, enzymatic production, and the techniques used to isolate and characterize these compounds. Furthermore, we review the methods used to assay the bioactivities and their applications in food and nutraceuticals.

Review: Production and functionality of active peptides from milk

In recent years, research on the production of active peptides obtained from milk and their potential functionality has grown, to a great extent. Bioactive peptides have been defined as specific protein fragments that have a positive impact on body functions or conditions, and they may ultimately have an influence on health. Individual proteins of casein or milk-derived products such as cheese and yogurt have been used as a protein source to study the isolation and activity of peptides with several applications. Currently, the milk whey waste obtained in the production of cheese also represents a protein source from which active peptides could be isolated with potential industrial applications. The active properties of milk peptides and the results found with regard to their physiological effects have led to the classification of peptides as belonging to the group of ingredients of protein nature, appropriate for use in functional foods or pharmaceutical formulations. In this study, the main peptides obtained from milk protein and the past research studies about its production and biological activities will be explained. Second, an analysis will be made on the methods to determinate the biological activities, the separation of bioactive peptides and its structure identification. All of these form the base required to obtain synthetic peptides. Finally, we explain the experimental animal and human trials done in the past years. Nevertheless, more research is required on the design and implementation of equipment for the industrial production and separation of peptides. In addition, different authors suggest that more emphasis should therefore be given to preclinical studies, proving that results are consistent and that effects are demonstrated repeatedly by several research human groups.

Antioxidant effect of a marine oligopeptide preparation from chum salmon (Oncorhynchus keta) by enzymatic hydrolysis in radiation injured mice

Marine oligopeptide preparation (MOP) obtained from Chum Salmon (Oncorhynchus keta) by the method of enzymatic hydrolysis, has been found to possess a radioprotective property through stimulation of the radiation-induced immunosuppression. The current study aimed to further investigate the free radicals scavenging and antioxidant effects of MOP in radiation injured mice. Female ICR mice (6-8 weeks old) were randomly divided into 5 groups, i.e., blank control, irradiation control and MOP (0.225, 0.450 and 1.350 g/kg body weight) plus an irradiation-treated group. The result revealed that MOP significantly increased the white blood cell counts after irradiation, and lessened the radiation-induced oxidative damage. These effects may be caused by augmentation of the activities of antioxidant enzymes, such as SOD and GSH-Px, reduction of the lipid peroxidation (MDA level) in liver, and protection against radiation-induced apoptosis. Therefore, we propose that MOP be used as an ideal antioxidant to alleviate radiation-induced oxidation damage in cancer patients.

Affinity purification and characterisation of chelating peptides from chickpea protein hydrolysates

A chickpea protein hydrolysate produced with pepsin and pancreatin was used for the affinity purification of chickpea chelating peptides. Three chelating peptide fractions were obtained after affinity chromatography with immobilised copper. These peptide fractions showed a higher chelating activity and histidine contents than the original protein hydrolysate. Chelating activity was positively correlated with the histidine content of the purified fractions. Different subfractions were also obtained after gel filtration chromatography from the affinity purified peptide fractions. Some of these subfractions showed a higher chelating activity and histidine contents than the original fractions. These results suggest that a combination of high His contents, around 20-30%, and small peptide size provide the best chelating activities. Thus sequential purification with affinity and gel filtration chromatography is a useful procedure for the purification of chickpea peptides with high chelating activity. These results show that a range of chelating peptides are generated during digestion of the chickpea proteins that, after metal chelation, may prevent the generation of reactive oxygen species (ROS) and favour metal absorption.

Extrusion texturized dairy proteins: processing and application

The primary proteins in milk, casein and the whey proteins α-lactalbumin and β-lactoglobulin, have a number of health benefits and desirable functional properties. In a twin-screw extruder, mechanical shear forces, heat, and pressure cause considerable changes in the molecular structures of the dairy proteins, a process known as texturization. These changes further impart unique functional properties to dairy proteins, resulting in new protein-based food ingredients. The new functional behavior depends on the extent of texturization and the degree of structural change imparted and is controlled by adjusting parameters such as extrusion temperature and moisture level. Such texturized proteins can be used to produce puffed high-protein snacks. Softer gels and expanded structures can be made using supercritical fluid extrusion and cold extrusion, techniques that avoid elevated temperatures, minimizing possible damage to the nutritive components and functionality of the texturized dairy proteins. The uses of the texturized dairy ingredient in food products with improved functionality and enhanced nutritive profiles are presented.

Identification and inhibitory properties of multifunctional peptides from pea protein hydrolysate

Pea protein isolate was hydrolyzed with alcalase, and the hydrolysate passed through a 1 kDa cutoff ultrafiltration membrane. The permeate was freeze-dried and fractionated on a cationic solid-phase extraction (SPE) column. All fractions were tested for their inhibitory activities against angiotensin-converting enzyme (ACE), renin, and calmodulin-dependent phosphodiesterase 1 (CaMPDE). With the exception of the first eluted fraction, inhibitory properties of the SPE fractions against CaMPDE (but not ACE and renin) were directly related to cationic character (residence time on the column). However, the fraction that eluted with 1% ammonium hydroxide (SPE 1%) had the highest peptide yield and was subsequently fractionated using two consecutive rounds of reversed-phase high-performance liquid chromatography to obtain three peaks with major peptides identified as IR, KF, and EF by ultra performance liquid chromatography-tandem mass spectrometry. The three dipeptides showed weak inhibitory properties toward CaMPDE but strong inhibitions (IC50 values <25 mM) of ACE and renin. In general, the peptides had higher potency against ACE than against renin. It is indicated from our results that these peptides may be used as potential ingredients to formulate multifunctional food products and nutraceuticals.

Protective effect of a marine oligopeptide preparation from chum salmon (Oncorhynchus keta) on radiation-induced immune suppression in mice

BACKGROUND

A marine oligopeptide preparation (MOP) obtained from Chum Salmon (Oncorhynchus keta) by the method of enzymatic hydrolysis, has been found to enhance the innate and adaptive immunities through stimulation of the secretion of cytokines in mice. The current study aimed to further investigate the protective effect of MOP on radiation-induced immune suppression in mice.

RESULTS

Female ICR mice (6-8 weeks old) were randomly divided into three groups, i.e. blank control, irradiation control and MOP (1.350 g kg(-1) body weight) plus irradiation-treated group. MOP significantly increased the survival rate and prolonged the survival times for 30 days after irradiation, and lessened the radiation-induced suppression of T- or B-lymphocyte proliferation, resulting in the recovery of cell-mediated and humoral immune functions. This effect may be produced by augmentation of the relative numbers of radioresistant CD(4) (+) T cells, enhancement of the level of immunostimulatory cytokine, IL-12, reduction of the level of total cellular NF-κB through the induction of IκB in spleen and inhibition of the apoptosis of splenocytes.

CONCLUSION

We propose that MOP be used as an ideal adjuvant therapy to alleviate radiation-induced injuries in cancer patients.

Identification of novel antioxidative peptides derived from a thermolytic hydrolysate of ovotransferrin by LC-MS/MS

Ovotransferrin is a glycoprotein well-known for its iron-binding property. Ovotransferrin was reported to have antioxidative properties, but the presence of antioxidant peptides within the protein has not been reported. The purpose of the study was to characterize the antioxidant peptides within ovotransferrin. Ovotransferrin was sonicated and hydrolyzed by thermolysin, and peptides from the hydrolysate were fractionated by ion-exchange fast protein liquid chromatography and reversed-phase high-performance liquid chromatography. Fourteen peptides derived from ovotransferrin were characterized using LC-MS/MS, and their oxygen radical absorbance capacity (ORAC) values were determined using synthetic peptides. Two tetrapeptides (Trp-Asn-Ile-Pro and Gly-Trp-Asn-Ile) showed the highest antioxidant activity. Interestingly, the addition of amino acid residues to either the N or C terminus of the two peptides decreased the antioxidant activity, suggesting that the motif of Trp-Asn-Ile is responsible for the high antioxidant activity.

Invited review: physiological properties of bioactive peptides obtained from whey proteins

Processing of whey proteins yields several bioactive peptides that can trigger physiological effects in the human body: on the nervous system via their opiate and ileum-contracting activities; on the cardiovascular system via their antithrombotic and antihypertensive activities; on the immune system via their antimicrobial and antiviral activities; and on the nutrition system via their digestibility and hypocholesterolemic effects. The specific physiological effects, as well the mechanisms by which they are achieved and the stabilities of the peptides obtained from various whey fractions during their gastrointestinal route, are specifically discussed in this review.

Use of a commercial protease and yeasts to obtain CGRP-like molecules from saithe protein

Different bioactive molecules, such as CGRP-like peptides, can be found in fish protein hydrolysates. Calcitonin gene-related peptide (CGRP) is a neuropeptide known to act as a potent arterial and venous vasodilator in humans. This study focuses on the industrial obtaining of CGRP-like molecules from saithe (Pollachius virens) byproduct, derived from the filleting process. Protein from P. virens was primarily hydrolyzed with Alcalase and later treated with Saccharomyces cerevisiae live cells. Treatment with Saccharomyces doubled the quantity of bioactive molecules obtained. The CGRP-like molecules were partially purified by chromatography, and the immunoreactive material was further analyzed for its CGRP-like bioactivity, using a specific radioreceptor assay. The concentration of CGRP-like molecules increased over 100-fold after purification. The bioactive molecules were able to induce cyclic AMP stimulation in rat liver membranes. Finally, partial sequencing of the bioactive peptide was performed, showing some homology with alpha-actin and myosin of several fish species.

Antihypertensive effect of an angiotensin converting enzyme inhibitory peptide from enzyme modified cheese

Two angiotensin converting enzyme (ACE)-inhibitory peptides were isolated from enzyme modified cheese (EMC) and their amino acid sequences were identified as Leu-Gln-Pro and Met-Ala-Pro. The EMC was prepared by a combination of Protease N, Umamizyme, and Flavourzyme 500L. Both peptides were derived from β-casein, f 88-90 and f 102-104, respectively. Met-Ala-Pro showed strong ACE inhibitory activity (IC50=0·8 μm) and antihypertensive activity in spontaneously hypertensive rats (SHR) after single oral administration. The IC50value of Met-Ala-Pro was not affected by pre-incubation with ACE, suggesting that this peptide was a true ACE-inhibitory peptide. We report here, for the first time antihypertensive peptides from EMC.

Proteolytic systems of lactic acid bacteria

Lactic acid bacteria (LAB) have a very long history of use in the manufacturing processes of fermented foods and a great deal of effort was made to investigate and manipulate the role of LAB in these processes. Today, the diverse group of LAB includes species that are among the best-studied microorganisms and proteolysis is one of the particular physiological traits of LAB of which detailed knowledge was obtained. The proteolytic system involved in casein utilization provides cells with essential amino acids during growth in milk and is also of industrial importance due to its contribution to the development of the organoleptic properties of fermented milk products. For the most extensively studied LAB, Lactococcus lactis, a model for casein proteolysis, transport, peptidolysis, and regulation thereof is now established. In addition to nutrient processing, cellular proteolysis plays a critical role in polypeptide quality control and in many regulatory circuits by keeping basal levels of regulatory proteins low and removing them when they are no longer needed. As part of the industrial processes, LAB are challenged by various stress conditions that are likely to affect metabolic activities, including proteolysis. While environmental stress responses of LAB have received increasing interest in recent years, our current knowledge on stress-related proteolysis in LAB is almost exclusively based on studies on L. lactis. This review provides the current status in the research of proteolytic systems of LAB with industrial relevance.

Strategies for designing novel functional meat products

In recent years, much attention has been paid to physiological functions of foods due to increasing concerns for health. Although there has been limited information of physiological functions of meat until recently, several attractive meat-based bioactive compounds, such as carnosine, anserine, l-carnitine, conjugated linoleic acid, have been studied. Emphasizing these activities is one possible approach for improving the health image of meat and developing functional meat products. This article provides potential benefits of representative meat-based bioactive compounds on human health and an overview of meat-based functional products. Strategies for designing novel functional meat products utilizing bioactive peptides and/or probiotic bacteria, is also discussed. This article focuses particularly on the possibility of meat protein-derived bioactive peptides, such as antihypertensive peptides. There are still some hurdles in developing and marketing novel functional meat products since such products are unconventional and consumers in many countries recognize meat and meat products to be bad for health. Along with accumulation of scientific data, there is an urgent need to inform consumers of the exact functional value of meat and meat products including novel functional foods.

Assessment of the immunomodulatory activity of cheese extracts by a complete and easy to handle in vitro screening methodology

A simple and rapid screening methodology based on the in vitro culture of murine hybridoma and human T-lymphocytes was developed to assess the potential immunomodulatory activity of water-soluble extracts (WSE) from cheese. The two immune cell lines were cultured in microplates with or without cheese WSE. The proliferation and the metabolic activity of cells were monitored at their different growth phases by the BrdU (5-bromo-2'-deoxyuridine) and MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylterazolium bromide] assays, respectively. WSE from Abondance cheese enhanced DNA synthesis and the metabolic activity of the hybridoma cells (1.2-and 1.3-to 1.6-fold of the control, respectively) and also of the T lymphocytes (1.5-fold of the control) for almost all of the dilutions tested. To evaluate the validity of the results obtained following this screening methodology, hybridoma and T-lymphocyte cells were cultivated in 50 ml flasks: the maximal cell density was increased by about 10-16% in presence of cheese WSE for both cell lines and the antibody production by the hybridoma cells was increased by 50%.

Mass spectrometric characterization of peptides derived by peptic cleavage of bovine β-casein

This study investigated the digestion of the milk protein beta-casein with pepsin under gastro-analogous conditions. Peptide sequences were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with post-source decay as well as liquid chromatography-tandem mass spectrometry by means of database searching. The new software tool, Mascot Distiller, improved the identification rate remarkably. In the case of small peptides, such as di- and tri-peptides, which are promising candidates for intestinal absorption and possible biological effects, identification was possible only after spectrum simulation and manual matching. A list of 41 identified peptides having 2-36 amino acids is given, and unexpected cleavage sites for pepsin are reported. Sequence coverage was 75%.