Bioactive milk peptides: a prospectus

The effects of dairy processes and storage on insulin-like growth factor-I (IGF-I) content in milk and in model IGF-I-fortified dairy products

The effects of several dairy processes on insulin-like growth factor-I (IGF-I) concentrations in milk and the storage stability of IGF-I-fortified dairy products were examined. The IGF-I content in raw milk determined by radioimmunoassay was significantly changed by the strength of heat treatments. In commercial manufacture of whole milk dry powder, IGF-I concentration was not significantly changed. A significant reduction in IGF-I content was found as the result of fermentation with a commercial starter culture. The IGF-I content in fortified milk and dried milk powder exhibited no significant changes over the tested storage periods (12 d for milk, 4 wk for dried milk powder), but the IGF-I content in the yogurt decreased significantly during storage. The use of IGF-I was varied by lactic strains and was apparent in the viable cells. When IGF-I was encapsulated using the surface-reforming process, the remaining IGF-I content after fermentation was significantly higher compared with that of the untreated control. Therefore, enteric coating of IGF-I before fermentation might be an effective method for the prevention of IGF-I degradation during fermentation.

Milk biologically active components as nutraceuticals: review

Milk contains components that provide critical nutritive elements, immunological protection, and biologically active substances to both neonates and adults. Milk proteins are currently the main source of a range of biologically active peptides. Concentrates of these peptides are potential health-enhancing nutraceuticals for food and pharmaceutical applications. Several bioactive peptides may be used as nutraceuticals, for example, in the treatment of diarrhea, hypertension, thrombosis, dental diseases, as well as mineral malabsorption, and immunodeficiency. Minor whey proteins, such as lactoferrin, lactoperoxidase, lysozyme, and immunoglobulins, are considered antimicrobial proteins. Milk also contains some natural bioactive substances. These include oligosaccharides, fucosylated oligosaccharides, hormones, growth factors, mucin, gangliosides, and endogenous peptides, which are present in milk at secretion. Most of the claimed physiological properties of milk bioactive components have been carried out in vitro or in animal model systems, and these hypothesized properties remain to be proven in humans. Whether these milk bioactive components will replace drugs entirely in the immediate future is still unclear, but the increasing appreciation of "drug foods" or nutraceuticals plays a complementary rather than a substitutional role to the synthetic pharmacological drugs.

Desempenho de bezerros alimentados com dietas líquidas à base de leite integral ou soro de leite

Quinze bezerros da raça Holandesa, desaleitados aos 30 dias de idade, foram utilizados para avaliar os efeitos da inclusão de fontes protéicas alternativas, em substituição às proteínas do leite integral, na formulação de sucedâneos do leite. Os animais foram divididos em três grupos: o grupo controle (C) - recebeu leite em pó integral reconstituído; o grupo sucedâneo SL (soro/leite) recebeu 41,6% da proteína bruta (PB) vinda do concentrado protéico de soro (CPS), 23,1% do soro de leite e 35,3% do leite em pó integral; e o grupo sucedâneo S (soro) recebeu 68% da PB vinda do CPS e 32% do soro de leite. O consumo de concentrado, feno, sal mineral e água foi mensurado diariamente, enquanto o ganho de peso foi avaliado semanalmente. Não houve diferença (P>0,05) para o consumo de concentrado, sal mineral e água entre os grupos, nos períodos avaliados. O consumo de feno e o ganho de peso foram inferiores nos animais do grupo S (P<0,05). A substituição de 100% do leite integral por CPS e soro de leite influenciou negativamente o desempenho.

Antibacterial activities of peptides from the water-soluble extracts of Italian cheese varieties

Water-soluble extracts of 9 Italian cheese varieties that differed mainly for type of cheese milk, starter, technology, and time of ripening were fractionated by reversed-phase fast protein liquid chromatography, and the antimicrobial activity of each fraction was first assayed toward Lactobacillus sakei A15 by well-diffusion assay. Active fractions were further analyzed by HPLC coupled to electrospray ionization-ion trap mass spectrometry, and peptide sequences were identified by comparison with a proteomic database. Parmigiano Reggiano, Fossa, and Gorgonzola water-soluble extracts did not show antibacterial peptides. Fractions of Pecorino Romano, Canestrato Pugliese, Crescenza, and Caprino del Piemonte contained a mixture of peptides with a high degree of homology. Pasta filata cheeses (Caciocavallo and Mozzarella) also had antibacterial peptides. Peptides showed high levels of homology with N-terminal, C-terminal, or whole fragments of well known antimicrobial or multifunctional peptides reported in the literature: alphaS1-casokinin (e.g., sheep alphaS1-casein (CN) f22-30 of Pecorino Romano and cow alphaS1-CN f24-33 of Canestrato Pugliese); isracidin (e.g., sheep alphaS1-CN f10-21 of Pecorino Romano); kappacin and casoplatelin (e.g., cow kappa-CN f106-115 of Canestrato Pugliese and Crescenza); and beta-casomorphin-11 (e.g., goat beta-CN f60-68 of Caprino del Piemonte). As shown by the broth microdilution technique, most of the water-soluble fractions had a large spectrum of inhibition (minimal inhibitory concentration of 20 to 200 microg/mL) toward gram-positive and gram-negative bacterial species, including potentially pathogenic bacteria of clinical interest. Cheeses manufactured from different types of cheese milk (cow, sheep, and goat) have the potential to generate similar peptides with antimicrobial activity.

Nutritional physiology of neonatal calves*

The gastrointestinal tract of neonatal calves is relatively mature but still requires morphological and functional changes. The intake of colostrum with its nutrient and non-nutrient components exerts marked effects on gastrointestinal development and function. Colostrum intake provides immunoprotection (passive immunity by immunoglobulins) and is essential for survival of neonates of most species. Furthermore, there are important transient as well as long-lasting systemic effects on the nutritional status, on metabolism, and on various endocrine systems due to intake of nutrient and non-nutrient colostral components that contribute to survival in the stressful postnatal period. Colostrum is much more than just a supplier of immunoglobulins.

Thermodynamics of Binding Interactions between Bovine β-Lactoglobulin A and the Antihypertensive Peptide β-Lg f142-148

The binding capacity of bovine beta-lactoglobulin variant A (beta-Lg A) for six peptides derived from beta-Lg was evaluated using an ultrafiltration method under the following conditions: pH 6.8, 40 degrees C, and a beta-Lg A/peptide molar ratio of 1:5. Only peptides beta-Lg f102-105, f142-148, and f69-83 bound in significant amounts to beta-Lg A corresponding to 1.5, 1.1, and 0.7 mol of peptide per mole of beta-Lg A, respectively. The interaction between beta-Lg A and the antihypertensive peptide beta-Lg f142-148 was investigated further by isothermal titration calorimetry. The binding isotherms at pH 6.8 and 25 degrees C confirmed that beta-Lg f142-148 bound to beta-Lg A and that the interaction followed a sequential three-site binding model with constants of association of 2 x 10(3), 1 x 10(3), and 0.4 x 10(3) M(-1) for the first, second, and third binding sites, respectively. The enthalpy of binding was exothermic for the first and second binding sites and endothermic for the third binding site. Binding of the peptide to all three sites was spontaneous as shown by the negative free energy values. These results show for the first time that beta-Lg A can bind bioactive peptides. This potential could be exploited to transport bioactive peptides and protect them in the gastrointestinal tract following their oral administration as nutraceuticals.

Effects of milk fermented by Lactobacillus helveticus R389 on immune cells associated to mammary glands in normal and a breast cancer model

Antitumour activity is an effect attributed to probiotics and fermented foods. Here, the immune cells in mammary glands and cytokine concentration in serum were analyzed using mice fed with milk fermented by Lactobacillus helveticus R389 or L89 (proteolytic-deficient variant), injected or not with breast tumour cells. Mice were fed 7 days with fermented milk, injected with breast tumour cells and 4 days post-injection, they received fermented milk. IgA, CD4, CD8, cytokines and Bcl-2 positive cells in mammary glands and cytokine in serum were determined. Mice fed with L. helveticus R389 fermented milk and injected with tumour cells increased IgA and CD4 positive cells in mammary glands (tumour control increased CD8 + cells). Mice from fermented milk control groups (without tumour cell injection) did not show changes in immune cell or cytokine positive cell numbers. IL-10 increases and IL-6 decreases were more pronounced in mice fed with milk fermented by L. helveticus R389 than in the other groups. This study demonstrated the immunoregulatory capacity of milk fermented by L. helveticus R389 on the immune response in mammary glands in presence of a local pathology (breast tumour). Orally administered fermented products could be used to modify the immune cell activation in distant mucosal sites and maintain these cells alert, but local stimulus was necessary to produce the activation of a local immune response in mammary glands, which could modulate the immune-endocrine relationship in these glands.

ACE inhibitory peptides derived from enzymatic hydrolysates of animal muscle protein: a review

Naturally occurring ACE (angiotensin converting enzyme) inhibitory peptides have a potential as antihypertensive components in functional foods or nutraceuticals. These peptides have been discovered in various food sources from plant and animal protein origin. In this paper an overview is presented of the ACE inhibitory peptides obtained by enzymatic hydrolysis of muscle protein of meat, fish, and invertebrates. Some of these peptides do not only show in vitro ACE inhibitory activity but also in vivo antihypertensive activity in spontaneously hypertensive rats. To focus on new sources of ACE inhibitory peptides, more specifically insects and other invertebrates, we compared the vertebrate and invertebrate musculature and analyzed phylogenetic relationships.

Structural Characteristics of Hydrolysates of Proteins from Extracted Sunflower Flour at the Air−Water Interface

The structural and topographical characteristics of a sunflower protein isolate (SPI) and its hydrolysates at different degrees of hydrolysis (DH = 5.62%, 23.5%, and 46.3%) spread at the air-water interface at pH 7 and 20 degrees C were determined from pi-A isotherms coupled with Brewster angle microscopy (BAM). The structural characteristics of SP hydrolysate spread monolayers depend on the degree of hydrolysis. We observed a significant shift of the pi-A(APPARENT) isotherms toward lower molecular areas as the degree of hydrolysis (DH) increased. This phenomenon was attributed to spreading of the protein at the interface, especially at DH 46.3%. A change in the monolayer structure was observed at a surface pressure of 12-15 mN/m. At a microscopic level, the heterogeneous monolayer structures visualized near the monolayer collapse and during the monolayer expansion proved the existence of large regions of protein aggregates. Reflectivity increased with surface pressure and was a maximum at the monolayer collapse. The monolayer thickness decreased as the degree of hydrolysis increased. These phenomena explain the poor functional properties for the formation and stabilization of a dispersion (emulsion or foam) of protein hydrolysates at high degrees of hydrolysis.

Effect of enzymatic treatment of extracted sunflower proteins on solubility, amino acid composition, and surface activity

Industrial proteins from agriculture of either animal or vegetable origin, including their peptide derivatives, are of great importance, from the qualitative and quantitative point of view, in food formulations (emulsions and foams). A fundamental understanding of the physical, chemical, and functional properties of these proteins is essential if the performance of proteins in foods is to be improved and if underutilized proteins, such as plant proteins (and their hydrolysates and peptides derivatives), are to be increasingly used in traditional and new processed food products (safe, high-quality, health foods with good nutritional value). In this contribution we have determined the main physicochemical characteristics (solubility, composition, and analysis of amino acids) of a sunflower protein isolate (SPI) and its hydrolysates with low (5.62%), medium (23.5%), and high (46.3%) degrees of hydrolysis. The hydrolysates were obtained by enzymatic treatment with Alcalase 2.4 L for DH 5.62 and 23.5% and with Alcalase 2.4 L and Flavorzyme 1000 MG sequentially for DH 46.3%. The protein concentration dependence on surface pressure (surface pressure isotherm), a measure of the surface activity of the products (SPI and its hydrolysates), was obtained by tensiometry. We have observed that the degree of hydrolysis has an effect on solubility, composition, and content of the amino acids of the SPI and its hydrolysates. The superficial activity and the adsorption efficiency were also affected by the degree of hydrolysis.

Fish and Shellfish Upgrading, Traceability

Recognition of the limited biological resources and the increasing environmental pollution has emphasised the need for better utilisation of by-products from the fisheries. Currently, the seafood industry is dependent on the processing of the few selected fish and shellfish species that are highly popular with consumers but, from economic and nutritional points of view, it is essential to utilise the entire catch. In this review, we will focus on recent developments and innovations in the field of underutilised marine species and marine by-product upgrading and, more precisely, on two aspects of the bioconversion of wastes from marine organisms, i.e. extraction of enzymes and preparation of protein hydrolysates. We will deal with the question of accurate determination of fish species at the various steps of processing. Methods of genetic identification applicable to fresh fish samples and to derived products will be described.

Identification of casein phosphopeptides released after simulated digestion of milk-based infant formulas

Adapted, follow-up, probiotic follow-up, toddler, and probiotic toddler infant formulas were subjected to an in vitro enzymatic procedure simulating physiological digestion. The formation and identification of casein phosphopeptides (CPPs) in the milk-based infant formulas were studied using reversed phase high-performance liquid chromatography coupled on line to an ion trap mass spectrometer. Most CPPs formed contained the cluster sequence SpSpSpEE, a mineral binding site. Phosphopeptide alpha(s2)-CN(1-19)4P was present in all formulas analyzed. Probiotic formulas released CPPs not detected in nonprobiotic formulas and probably formed by bifidobacteria action. These observations suggest that physiological digestion of these products promotes the formation of bioactive peptides with mineral carrier properties in the gastrointestinal tract, which resist further proteolysis.

Angiotensin I converting enzyme inhibitory peptides from in vitro pepsin-pancreatin digestion of soy protein

Angiotensin I converting enzyme (ACE) inhibitory activity was determined in the soy protein isolate (SPI) digest produced by in vitro pepsin-pancreatin sequential digestion. The inhibitory activity was highest within the first 20 min of pepsin digestion and decreased upon subsequent digestion with pancreatin. An IC(50) value of 0.28 +/- 0.04 mg/mL was determined after 180 min of digestion, while no ACE inhibitory activity was measured for the undigested SPI at 0.73 mg/mL. Chromatographic fractionation of the SPI digest resulted in IC(50) values of active fractions ranging from 0.13 +/- 0.03 to 0.93 +/- 0.08 mg/mL. Although many of the fractions showed ACE inhibition, peptides with lower molecular masses and higher hydrophobicities were most active. The findings show that many different peptides with ACE inhibitory activities were produced after in vitro pepsin-pancreatin digestion of SPI and lead to the speculation that physiological gastrointestinal digestion could also yield ACE inhibitory peptides from SPI.

Speciation analysis of calcium, iron, and zinc in casein phosphopeptide fractions from toddler milk-based formula by anion exchange and reversed-phase high-performance liquid chromatography?mass spectrometry/flame atomic-absorption spectroscopy

Casein phosphopeptides (CPP) are phosphorylated casein-derived peptides that can be released by in-vitro or in-vivo enzymatic hydrolysis of alpha(s1)-casein, alpha(s2)-casein, and beta-casein (CN). Many of these peptides contain a highly polar acidic sequence of three phosphoseryl groups followed by two glutamic acid residues. These domains are binding sites for minerals such as calcium, iron, and zinc and play an important role in mineral bioavailability. The aim of this study was speciation analysis of calcium, iron, and zinc in CPP fractions from the soluble fraction of a toddler milk-based formula. Methods for CPP separation by anion-exchange high-performance liquid chromatography (AE-HPLC) were combined with CPP identification by reversed-phase high performance liquid chromatography-electrospray ionization mass spectrometry and determination of the calcium, iron, zinc, and phosphorus content of the fractions obtained by AE-HPLC. Calcium and phosphorus were detected in all the analyzed AE-HPLC fractions. Calcium and zinc could be bound to CPP derived from alpha(s1)-CN and alpha(s2)-CN in fraction 3. Iron could be bound to CPP in fraction 4 in which beta-CN(15-34)4P was present with the cluster sequence S(P)S(P)S(P)EE. The results obtained prove the different distribution of calcium, iron, and zinc in heterogeneous CPP fractions.

Expression and bioactivity analysis of recombinant beta-CPP dimer

Beta-casein phosphopeptide (beta-CPP) is a bioactive peptide that carries different minerals, especially calcium. To investigate more effects of beta-CPP, eukaryotic expression vector of beta-CPP dimer was constructed and transfected into Chinese hamster ovary (CHO) cells. After selection, the cell lines stably expressing beta-CPP dimer were obtained, and the recombinant product was identified and purified. Activity assay of recombinant protein indicated that the recombinant beta-CPP dimer could improve Ca(2+) uptake of sperm, stimulate the proliferation of spleen cells, and induce apoptosis of some malignant tumor cells.

Effects of a tryptic hydrolysate from bovine milk αS1–casein on hemodynamic responses in healthy human volunteers facing successive mental and physical stress situations

BACKGROUND

Preclinical results in rats have demonstrated anxiolytic-like effects of a tryptic bovine alphaS1-casein hydrolysate.

AIM OF THE STUDY

We investigated the putative effects of this tryptic hydrolysate on systolic (SBP), diastolic (DBP) blood pressures, heart rate (HR) values and plasma cortisol concentrations (CC) in human healthy volunteers facing successive stress situations.

METHODS

The subjects were (double blind) randomly allocated to ingest three times, 12 hours apart, two capsules containing either 200 mg of alphaS1-casein hydrolysate (TS) or bovine skimmed milk powder as a placebo (CS). On the morning of the test day, a first blood sample for baseline measurement of CC was taken before the subjects were submitted to the Stroop test (ST) and, after a 30-min rest, to a Cold Pressor test (CPT). SBP, DBP, and HR were continuously recorded for 5 min before the ST and during each stress situation. A second blood sample was taken 15 min after the end of the CPT condition.

RESULTS

ST and ST + CPT combined test situations increased SBP, DBP and HR. The significant "Treatment x SBP" and "Treatment x DBP" interactions indicated the lower percentage changes in SBP and DBP of the TS. In addition, the results showed a significant decrease of the CC in the TS but not in the CS throughout the ST + CPT combined stress tests. HR remained stable in TS between the initial rest period and the CPT unlike what happened in CS.

CONCLUSION

On the basis of blood pressure and cortisol changes, these results suggest an antistress profile of this alphaS1-casein hydrolysate in human subjects.

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%.

Induction of a humoral immune response following an Escherichia coli O157:H7 infection with an immunomodulatory peptidic fraction derived from Lactobacillus helveticus-fermented milk

Numerous beneficial effects have been attributed to probiotic lactic acid bacteria (LAB), such as the stimulation of the immune system, the prevention of enteric infections by enteropathogens, and the regression of immunodependent tumors. It has been shown that biologically active metabolites released during fermentation, in particular biopeptides, could act as immunomodulatory agents. However, no studies have been conducted to evaluate the implication of these bioactive peptides in the induction of a protective immune response against enteric infections. The present study aimed to evaluate the possible immunomodulatory and anti-infectious effects of a peptidic fraction released in milk fermented by Lactobacillus helveticus. The immune response in the mucosa-associated lymphoid tissue was monitored following an administration of the potentially bioactive peptidic fraction. The total immunoglobulin A (IgA) immune response was evaluated after an Escherichia coli O157:H7 infection in a BALB/c murine model. Immunohistochemical and enzyme-linked immunosorbent assays revealed an increase in the number of IgA-secreting B lymphocytes in the intestinal lamina propria and an enhanced total secretory and systemic IgA response. Cytokine profiling also revealed stimulation of a Th2 response in mice fed the peptidic fraction, whereas infected controls demonstrated a proinflammatory Th1 response. These results indicate that bioactive peptides released during fermentation by LAB could contribute to the known immunomodulatory effects of probiotic bacteria.

Purification and characterization of an endopeptidase that has an important role in the carboxyl terminal processing of antihypertensive peptides in Lactobacillus helveticus CM4

AIMS

To purify and characterize a peptidase that can catalyse C-terminal processing of antihypertensive peptide from Lactobacillus helveticus CM4.

METHODS AND RESULTS

An endopeptidase which seems to process the carboxyl terminal end of two antihypertensive peptides, Val-Pro-Pro and Ile-Pro-Pro, was purified from Lactobacillus helveticus CM4 by four stages of column chromatography, using synthetic pro-peptide as a substrate. The molecular weight of the purified enzyme was estimated to be 67,000 by SEPHACRYL S-200 and 70,000 by SDS-PAGE analysis. The purified enzyme generated: (i) Val-Pro-Pro from Val-Pro-Pro-Phe-Leu and Val-Pro-Pro-Phe-Leu-Gln-Pro, and (ii) Ile-Pro-Pro from Ile-Pro-Pro-Leu-Thr and Ile-Pro-Pro-Leu-Thr-Gln-Thr, but theses peptides could not be generated from Val-Pro-Pro-Phe, Val-Pro-Pro-Phe-Leu-Gln, Ile-Pro-Pro-Leu and Ile-Pro-Pro-Leu-Thr-Gln. Part of the amino terminal sequence of the purified enzyme had homology to a previously reported pepO gene product.

CONCLUSION

These results suggest that the purified endopeptidase isolated in this study have an important role in the carboxyl terminal processing of two antihypertensive peptides in Lact. helveticus CM4.

Modification of the furanacryloyl-l-phenylalanylglycylglycine assay for determination of angiotensin-I-converting enzyme inhibitory activity

Angiotensin-I-converting enzyme (ACE, EC 3.4.15.1) plays a central role in the regulation of blood pressure in man. The objective of this study was to evaluate and modify the furanacryloyl-L-phenylalanylglycylglycine (FAPGG) assay method for quantification of ACE activity. The fixed time conditions developed for assay of ACE activity were as follows: 0.8 mM FAPGG, 175 + or - 10 units l(-1) ACE, incubation at 37 degrees C for 30 min and enzyme inactivation with 100 mM ethylenediaminetetra-acetic acid (EDTA). Hydrolysis of FAPGG to FAP and GG was quantified by measuring the decrease in absorbance at 340 nm. It was shown that increasing the level ACE activity in the assay from 155 to 221 + or - 15 units l(-1) resulted in a corresponding increase in the apparent IC(50) value for Captopril from 9.10 to 39.40 nM. Similar trends in the apparent IC50 values for a whey protein hydrolysate were obtained. The results demonstrate the requirement for carefully controlling ACE activity levels in the assay in order to obtained comparable and reproducible values for the inhibitory potency of ACE inhibitors.

Peptides from milk proteins and their properties

This review has attempted to study the literature pertaining to peptides derived from milk proteins. Hydrolysis of milk proteins to generate peptides has been practiced for a long time and it was recognized early on in this process that the taste of hydrolyzates might hinder use of these products in food formulations. Modification of protein is necessary to form a more acceptable or utilizable product, to form a product that is less susceptible to deteriorative reactions and to form a product that is of higher nutritionall quality. Modifications may be achieved by a number of chemical and enzymatic means. This review has considered only enzymatic modification of dairy proteins. Modified proteins contain peptides and some of these peptides have been purified and their functionalities have been compared with unmodified proteins. This paper has examined the literature pertaining to improvement in functionality of enzyme-modified proteins. Improvements in solubility, emulsification, foaming and gelation were examined. There is limited information available on the sequence of the peptides necessary to improve the functional characteristics of proteins. Knowing the sequences of desirable functional peptides can lead to genetic alteration of proteins to improve functionality. Addition of synthetic peptides to intact proteins may be another way in which the functionality of proteins can be augmented. Some of the peptides in milk proteins are capable of affecting biological functions of an organism. These effects can be antimicrobial and probiotic, i.e., prevent the growth and proliferation of undesirable and pathogenic organisms, or they may promote the growth of desirable bacteria in the digestive tract of humans and animals. Peptides derived from milk protein have been shown to exert digestive and metabolic effects as well. They may also influence the immune system. These biological effects may play an important role in the development of medical foods that treat or mitigate the effects of diseases. Proteins are allergens and therefore it is possible that products derived from modification of proteins may also be allergens. The known literature about the allergenicity of peptides derived from milk proteins has been examined in this article. Last, but not the least, the taste attributes of peptides is also considered. Bitterness of hydrolyzates is a common occurrence and the origins of these bitter peptides and possible ways of mitigating this sensory defect has been discussed. Many of the peptides that enhance functionality and exert biological activity are likely to be bitter. Therefore, the bitter taste of hydrolysis products has to be dealt with in boosting the functional or nutraceutical aspects of foods containing these peptides. Analytical techniques for sequencing peptides have become more accessible and purification of peptides is commercially feasible. Computer based modeling techniques have aided the prediction of structures in these peptides. These advances, coupled with the advances in biotechnology, promise to revolutionize the future of nutraceutical and functional foods.

Purification of an ACE inhibitory peptide after hydrolysis of sunflower (Helianthus annuus L.) protein isolates

Sunflower protein isolates and the proteases pepsin and pancreatin were used for the production of protein hydrolysates that inhibit angiotensin-I converting enzyme (ACE). Hydrolysates obtained after 3 h of incubation with pepsin and 3 h with pancreatin were studied. An ACE inhibitory peptide with the sequence Phe-Val-Asn-Pro-Gln-Ala-Gly-Ser was obtained by G-50 gel filtration chromatography and high-performance liquid chromatography C18 reverse phase chromatography. This peptide corresponds to a fragment of helianthinin, the 11S globulin from sunflower seeds, which is the main storage protein in sunflower. These results show that sunflower seed proteins are a potential source of ACE inhibitory peptides when hydrolyzed with pepsin and pancreatin.

Sodium caseinate induces expression and secretion of murine multipotent myeloid cell line 32D macrophage colony-stimulating factor

BACKGROUND

Evidence that sodium caseinate (CasNa) is capable of inhibiting proliferation of hematopoietic precursor cell line 32D and inducing its differentiation into macrophage cells has recently been published. Taking into consideration that hematopoiesis is regulated by growth factors and that macrophage colony-stimulating factor (M-CSF) is a well-known growth factor that induces differentiation of macrophages, in this work we evaluated whether CasNa is capable of inducing expression and secretion of M-CSF in 32D cells.

METHODS

We cultured 32D cells in presence and absence of CasNa and compared their proliferation and viability. RNA was extracted from cell lysates to evaluate expression of the gene for M-CSF and its receptor. Cultured conditioned media was used to evaluate presence of M-CSF.

RESULTS

Our results showed that CasNa inhibited proliferation of 32D cells and that conditioned media (CM) of these cultures contained M-CSF-like activity. Presence of M-CSF in CM was detected by inhibiting M-CSF activity with anti-M-CSF and presence of this growth factor was confirmed by ELISA assay. We also provided evidence that CasNa induced expression of mRNA for M-CSF in 32D cells as well as increased expression of mRNA for its receptor.

CONCLUSIONS

CasNa inhibits proliferation of 32D cells and induces expression of the gene for M-CSF and that of its receptor. It also induces secretion of the bioactive form of M-CSF.

Multifunctional peptides encrypted in milk proteins

Many bioactivities of milk are latent in that they are inactive within the protein sequence, requiring enzymatic proteolysis for release of bioactive peptides from milk proteins precursors. Bioactivities of peptides encrypted in major milk proteins are latent until released and activated, e.g. during gastrointestinal digestion or food processing. Bioactive peptides can be produced in vivo following intake of milk proteins, and the proteolytic system of bacterial species used in the production of fermented milk products and cheese can contribute to the liberation of bioactive peptides or precursors thereof. Activated peptides are potential modulators of various regulatory processes in the living system: immunomodulatory peptides stimulate the activities of cells of the immune system and several cytomodulatory peptides inhibit cancer cell growth, antimicrobial peptides kill sensitive microorganisms, angiotensin-I-converting enzyme (ACE)-inhibitory peptides exert an hypotensive effect, opioid peptides are opioid receptor ligands which can modulate absorption processes in the intestinal tract, mineral binding peptides may function as carriers for different minerals, especially calcium. Many milk-derived peptides reveal multifunctional properties, i.e. specific peptide sequences having two or more different biological activities have been reported. Milk protein-derived bioactive peptides are claimed to be health enhancing components that can be used to reduce the risk of disease or to enhance a certain physiological function.

Contribution of beverages to the intake of lipophilic and hydrophilic antioxidants in the Spanish diet

OBJECTIVE

To investigate the contribution of beverages to the intake of lipophilic and hydrophilic antioxidants in the Spanish diet.

DESIGN

This includes the following (i) estimation of the daily intakes of beverages in Spain, from national food consumption data obtained from annual surveys of 5400 households, 700 hotels and restaurants and 200 institutions; (ii) determination of total antioxidant capacity in the selected beverages using two complementary procedures: ferric reducing ability of plasma (FRAP), which measures the ferric reduction capacity, and ABTS, which measures the radical scavenging capacity; (iii) determination of the antioxidant capacity in both lipophilic and hydrophilic extracts of the beverages; (iv) determination of the antioxidant efficiency of the lipophilic and hydrophilic phase of the beverages; and (v) estimation of the intake of dietary antioxidants from beverages in comparison with the daily requirements of antioxidant vitamins C and E.

RESULTS

The contribution of beverages to the antioxidant intake in the Spanish diet is estimated at 1623 mg of vitamin E and 598 mg of vitamin C by FRAP, and 1521 mg of vitamin E and 556 mg of vitamin C by ABTS. Coffee is the main contributor (66 and 61% by FRAP and ABTS, respectively), followed by red wine (16 and 22%), fruit juices (6 and 5%), beer (4 and 5%), tea (3 and 5%) and milk (4 and 1%).

CONCLUSIONS

Beverages account for a very high proportion of dietary antioxidant intake as compared to intake of antioxidant vitamins C and E. Although their metabolic effect must be affected by the bioavailability of the antioxidants, the significance of this intake for antioxidant status and health should be considered.

Angiotensin I-converting-enzyme-inhibitory and antibacterial peptides from Lactobacillus helveticus PR4 proteinase-hydrolyzed caseins of milk from six species

Sodium caseinates prepared from bovine, sheep, goat, pig, buffalo or human milk were hydrolyzed by a partially purified proteinase of Lactobacillus helveticus PR4. Peptides in each hydrolysate were fractionated by reversed-phase fast-protein liquid chromatography. The fractions which showed the highest angiotensin I-converting-enzyme (ACE)-inhibitory or antibacterial activity were sequenced by mass spectrum and Edman degradation analyses. Various ACE-inhibitory peptides were found in the hydrolysates: the bovine alpha(S1)-casein (alpha(S1)-CN) 24-47 fragment (f24-47), f169-193, and beta-CN f58-76; ovine alpha(S1)-CN f1-6 and alpha(S2)-CN f182-185 and f186-188; caprine beta-CN f58-65 and alpha(S2)-CN f182-187; buffalo beta-CN f58-66; and a mixture of three tripeptides originating from human beta-CN. A mixture of peptides with a C-terminal sequence, Pro-Gly-Pro, was found in the most active fraction of the pig sodium caseinate hydrolysate. The highest ACE-inhibitory activity of some peptides corresponded to the concentration of the ACE inhibitor (S)-N-(1-[ethoxycarbonyl]-3-phenylpropyl)-ala-pro maleate (enalapril) of 49.253 micro g/ml (100 micro mol/liter). Several of the above sequences had features in common with other ACE-inhibitory peptides reported in the literature. The 50% inhibitory concentration (IC(50)) of some of the crude peptide fractions was very low (16 to 100 micro g/ml). Some identified peptides were chemically synthesized, and the ACE-inhibitory activity and IC(50)s were confirmed. An antibacterial peptide corresponding to beta-CN f184-210 was identified in human sodium caseinate hydrolysate. It showed a very large spectrum of inhibition against gram-positive and -negative bacteria, including species of potential clinical interest, such as Enterococcus faecium, Bacillus megaterium, Escherichia coli, Listeria innocua, Salmonella spp., Yersinia enterocolitica, and Staphylococcus aureus. The MIC for E. coli F19 was ca. 50 micro g/ml. Once generated, the bioactive peptides were resistant to further degradation by proteinase of L. helveticus PR4 or by trypsin and chymotrypsin.

Angiotensin-I-converting enzyme inhibitory peptides from tryptic hydrolysate of bovine alphaS2-casein

Angiotensin-I-converting enzyme (ACE) inhibitory activity of a tryptic digest of bovine alpha(S2)-casein (alpha(S2)-CN) was extensively investigated. Forty-three peptide peaks were isolated and tested. Seven casokinins (i.e. CN-derived ACE inhibitory peptides) were identified and their IC50 values were determined. Four peptides exhibited an IC50 value lower than 20 microM. Peptides alpha(S2)-CN (f174-181) and alpha(S2)-CN (f174-179) had IC50 values of 4 microM. Surprisingly, deletion of the C-terminal dipeptide of two of these casokinins did not significantly alter their inhibitory activity.

Bioactive components in milk

Milk is the only biomaterial that evolved under the Darwinian selective pressure to nourish growing mammals. The purpose of this article is to review the scientific research that is using new techniques of integrating biological sequence, structure and function, to understand the innovative biology underlying the products of that evolutionary pressure. As it emerges that milk is actively communicating between the maternal mammary epithelia and the infant's gastrointestinal system, actively directing and educating the immune, metabolic and microflora systems within the infant, enhancing nutrient absorption and delivery, and conferring multiple means of protection, nutritionists are gaining a host of new molecular targets towards which to build scientific strategies for future foods and clinical applications. As new components and functions are being discovered in milk by using traditional methods and modern genomic tools, the complexities of demonstrating, and particularly in humans, the functional mechanisms behind milk's newly observed physiological benefits are becoming the next challenge of this rapidly growing field.

Bioavailability of caseinophosphopeptide-bound iron

Iron deficiency, one of the main worldwide nutritional deficiencies, results from the low bioavailability of most dietary iron, including cow milk. Hydrolysis of the cow milk protein casein produces low molecular weight caseinophosphopeptides (CPPs). Binding of iron to CPPs keeps it soluble in the digestive tract and prevents the formation of high molecular weight ferric hydroxides, which are poorly absorbed. Previous experimental studies have shown that iron bound to the phosphopeptide containing the first 25 amino acids of beta-casein, or beta-CN (1-25), is well absorbed and corrects efficiently iron deficiency. We sought to assess in vivo iron absorption and uptake by tissues involved in iron metabolism and storage (liver, spleen, bone marrow), using radiolabeled iron. beta-CN (1-25)-Fe displayed better absorption and tissue uptake by the vascularized rat loop model compared with a control substance, ferric ascorbate. The metabolism of beta-CN (1-25)-Fe labeled with iron 59, added to cow milk, was also studied in young women. Although the absorption of beta-CN (1-25)-Fe was not significantly higher than that of ferrous sulfate, it displayed significantly higher tissue uptake. This increase was transient and had disappeared by the 14th day of the study, suggesting that iron was used for metabolic purposes.

Characterization and expression of L-amino acid oxidase of mouse milk

l-Amino acid oxidase (LAO) was purified from mouse milk. LAO reacted with l-amino acids in an apparent order of Phe > Met, Tyr > Cys, Leu > His other 11 amino acids tested and produced H(2)O(2) in a dose- and time-dependent manner. LAO in milk had a molecular mass of about 113 kDa and was converted to a 60-kDa protein by SDS-PAGE. LAO consisted of two subunits. The N- and C-terminal amino acid sequence determination followed by cDNA cloning showed that the 60-kDa protein consisted of 497 amino acids. LAO mRNA spanned about 2.0 kb, and its expression was found only in the mammary epithelial cells. Glucocorticoid was essential for LAO gene expression. Thus, the LAO gene is expressed acutely upon the onset of milk synthesis. LAO mRNA increased 1 day before parturition, peaked during early to mid-lactation, and decreased at the end of lactation. This is the first demonstration showing that LAO is present in milk. Mastitis is caused by an intramammary bacterial infection. As mouse milk produced H(2)O(2) using endogenous free amino acids, we suggest that LAO, together with free amino acids, is responsible for killing bacteria in the mammary gland.