Isolation and characterization of four bactericidal domains in the bovine beta-lactoglobulin

Bovine hemoglobin: an attractive source of antibacterial peptides

A peptic hemoglobin hydrolysate was fractioned by a semi-preparative reversed-phase HPLC and some fractions have an antibacterial activity against four bacteria strains: Micrococcus luteus A270, Listeria innocua, Escherichia coli and Salmonella enteritidis. These fractions were analyzed by ESI/MS and ESI/MS/MS, in order to characterize the peptides in these fractions. Each fraction contains at least three peptides and some fractions contain five peptides. All these fractions were purified several times by HPLC to obtain pure peptides. Thirty antibacterial peptides were identified. From the isolated antibacterial peptides, 24 peptides were derived from the alpha chains of hemoglobin and 6 peptides were derived from the beta chains of hemoglobin. The lowest concentration of these peptides (minimum inhibitory concentration (MIC)) necessary to completely inhibit the growth of four bacteria strain was determined. The cell population of all of the tested bacteria species decreased by at least 97% after a 24-h incubation with any of the peptides at the minimum inhibitory concentration.

Antimicrobial properties of milkfat globule membrane fractions

Milkfat globule membranes (MFGMs) were prepared from bovine cream according to standard procedures. These membranes and peptide hydrolysates, which were generated by proteolysis with immobilized digestive enzymes, were screened for antibacterial activity against Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica Typhimurium, Pseudomonas fluorescens, Bacillus cereus, Lactobacillus acidophilus, and Lactobacillus gasseri. Assays were first performed on beef heart infusion (BHI) plates spotted with test protein-peptide fractions and then seeded with lawns of indicator cells to monitor the zone of growth inhibition. Under these experimental conditions, MFGMs were most active against Salmonella Typhimurium and P. fluorescens. However, antibacterial activity was not seen after plating on Luria-Bertani (LB) medium. We determined that the antimicrobial effects observed on BHI plates were due to the generation of H2O2 by xanthine oxidase, a major protein constituent of the MFGMs, as a result of purine catalysis. This substrate is present in BHI but lacking in LB medium. Evaluation of purified xanthine oxidase alone resulted in analogous data trends. The growth of probiotic Lactobacillus strains were affected only marginally when grown on lactobacilli deMan Rogosa Sharpe plates, suggesting the decreased sensitivity of these bacteria to H2O2. In this study, several MFGM hydrolysates exhibited variable antibacterial activity against test food pathogens on agar plates prepared with M9 minimal media, and this variation was not attributable to xanthine oxidase enzymatic activity. The probiotic microorganisms were mostly resilient to these antibacterial fractions. Bovine MFGM fractions may represent an excellent resource material from which to generate native, naturally occurring biodefensive proteins and/or peptides.

A proteomic approach to analysis of antimicrobial activity in marsupial pouch secretions

We have documented the antimicrobial activity of pouch secretions of the tammar wallaby, Macropus eugenii, over the period leading up to birth and after birth of the young animal. This activity was greatest against the Gram-negative Escherichia coli and highest at the time of birth. Fractionation of the pouch secretions showed that activity at different times over the reproductive periods was associated with different molecular-weight (MW) components, with compounds in the range up to 50 kDa active immediately prior to and at the time of birth. Proteomic analysis using 1 and 2DE PAGE and LC-MS/MS identified the major components of the pouch secretions at these times, at a range of pI's and MWs. The majority of high-confidence identifications, at a wide range of pI's and MW, were beta-lactoglobulin, a known component of marsupial milk. We subsequently conducted a proteomic analysis of mammary gland secretions and digest products from the gut of the young animal, using 2DE PAGE and MALDI MS/MS, to confirm its source and compare it with the observed MW and pI's of beta-lactoglobulin. Although we did not directly identify an effector molecule responsible for antimicrobial activity, these results lead us to propose that beta-lactoglobulin plays a role in the protection of the young marsupial, a role previously thought to be primarily due to specific secretions from the epithelial surface of the pouch.

β-Lactoglobulin as source of bioactive peptides

Beta-lactoglobulin (beta-Lg) is currently an important source of biologically active peptides. These peptides are inactive within the sequence of the precursor protein, but they can be released by in vivo or in vitro enzymatic proteolysis. Once released, these peptides play important roles in the human health, including antihypertensive, antioxidant and antimicrobial activities as well as opioid-like features and ability to decrease the body-cholesterol levels. Bioactive peptides derived from beta-Lg are currently a point of intensive research. Their structure, biological significance and mechanism of action are briefly presented and discussed in this review.

Identification of antibacterial peptides from bovine kappa-casein

The objective of the present study was to identify antimicrobial peptides present in several digests of commercial caseins with gastric enzymes. The most active hydrolysate against Escherichia coli ATCC 25922 and Listeria innocua CECT 910T corresponded to a pepsin digest of bovine kappa-casein. The protein digest was first separated by semipreparative high-performance liquid chromatography (HPLC), and the most active fractions were again subjected to a second chromatographic step. Finally, identification of the active peptides was carried out by online and offline HPLC-electrospray ionization-tandem mass spectrometry. By means of this technique, 21 peptides were identified in the active HPLC fractions. Although most were derived from bovine kappa-casein, some of the identified fragments corresponded to beta-casein and alpha(s)-casein fragments, a result of the presence of small amounts of these proteins in the preparation of kappa-casein. Some of the peptides identified were chemically synthesized and showed antibacterial effects against several gram-positive and gram-negative bacteria. Among the synthesized peptides, kappa-casein f(18-24), f(30-32), and f(139-146) were most effective against all bacteria tested. The antibacterial effect of these peptides is discussed in relation to their amino acid sequences.

Structure of bovine β-lactoglobulin (variant A) at very low ionic strength

Bovine beta-lactoglobulin (BLG) is a globular protein of uncertain physiological function and a member of the lipocalin superfamily of proteins. Here, we present the X-ray structure at 3.0 angstroms of BLG (variant A) from an orthorhombic (P2(1)2(1)2(1)) pseudo-tetragonal crystal form that suffers from pseudo-merohedral twinning (final R(working) = 0.224, R(free) = 0.265). Crystals were grown by dialysis against ultra-purified water (i.e., at very low ionic strength), at pH approximately 5.2 (approximately pI), conditions vastly different from all other BLG structures determined previously. This allows critical assessment of the BLG structure and of the influence that pH, ionic strength, and crystal packing may have on the molecular structure of BLG. The pH-sensitive EF loop is found in the closed conformation characteristic of BLG at pH less than 7 and moderate to high ionic strength. Although the hydrophobic pocket appears to be empty, the presence of highly disordered water molecules cannot be excluded. The dimer interface and the hydrophobic pocket (calyx) are preserved. However, the orientation of the subunits in the dimer varies considerably with crystal form. Structure is deposited with PDB ID 2akq.

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.

Simultaneous separation of acid and basic bioactive peptides by electrodialysis with ultrafiltration membrane

beta-Lactoglobulin (beta-lg), one of the major whey components, can release by enzymatic hydrolysis different bioactive peptidic sequences according to the enzyme used. However, these protein hydrolysates have to be fractionated to obtain peptides in a more purified form. The aim of the present work was to evaluate the feasibility of separating peptides from a beta-lg hydrolysate using an ultrafiltration (UF) membrane stacked in an electrodialysis (ED) cell and to study the effect of pH on the migration of basic/cationic and acid/anionic peptides in the ED configuration. Electrodialysis with ultrafiltration membrane (EDUF) appeared to be a selective method of separation since amongst a total of 40 peptides in the raw hydrolysate, only 13 were recovered in the separated adjacent solutions (KCl 1 and KCl 2). Amongst these 13 migrating peptides, 3 acid/anionic peptides migrated only in one compartment (KCl 1), while 3 basic/cationic peptides migrated only in the second compartment (KCl 2) and that whatever the pH conditions of the hydrolysate solution. Furthermore, the highest migration was obtained for the ACE-inhibitory peptide beta-lg 142-148, with a value of 10.75%. The integrity of the UF membrane was kept and EDUF would minimize the fouling of UF membrane.

Whey proteins and peptides: beneficial effects on immune health

A 65-year-old male with liver metastases after lung cancer resection was treated with five courses of chemotherapy consisting of gemcitabine (GEM) 1,000 mg/m2 (day 1, 8, every 4 weeks) plus carboplatin (CBDCA) AUC 6 (day 1, every 4 weeks). A partial response (PR) was achieved, his symptoms abated and his quality of life(QOL) improved. Although bone marrow suppression was observed as a side effect, it was within the tolerable range and did not interfere with therapy. This approach may be worth considering as a first-line anti-cancer chemotherapy for recurrence lung cancer.

Propriedades fisiológicas-funcionais das proteínas do soro de leite

O presente artigo coloca em destaque as propriedades multifuncionais das proteínas presentes no soro de leite bovino, a começar pelo colostro que contém essas proteínas em concentrações muito elevadas e que tem por função garantir a proteção e a imunidade dos recém-nascidos. Essas mesmas proteínas continuam no leite, porém em concentrações bastante reduzidas. A utilização dessas proteínas nas formas de concentrados e isolados protéicos evidenciam propriedades muito favoráveis à saúde no sentido de diminuir o risco de doenças infecciosas e também as consideradas crônicas e/ou degenerativas. Enfatizou-se as propriedades das proteínas do soro de leite e de peptídios delas resultantes no estímulo ao sistema imunológico, na proteção contra microrganismos patogênicos e contra alguns tipos de vírus como o HIV e o vírus da hepatite C, na proteção contra vários tipos de câncer, particularmente de cólon, na proteção da mucosa gástrica contra agressão por agentes ulcerogênicos, evidenciou-se várias linhas de ação protetora das proteínas de soro contra agentes condicionadores de problemas cardiovasculares. Com base em várias propriedades funcionais das proteínas do soro de leite, discutiu-se a vantagem e os benefícios de seu uso como suplemento alimentar para atletas e esportistas em geral. Os possíveis benefícios de vários fatores de crescimento celular, presentes no soro de leite também foram discutidos.

Proteolytic fragments of ovalbumin display antimicrobial activity

Ovalbumin, one of the major proteins present in avian egg white, was proteolytically digested by trypsin and chymotrypsin and the peptide fragments were investigated for their antimicrobial activity. The antimicrobial peptides were isolated and characterized. From the tryptic digestion, the following five antimicrobial peptide fragments were obtained: SALAM (residues 36-40), SALAMVY (residues 36-42) YPILPEYLQ (residues 111-119), ELINSW (residues 143-148) and NVLQPSS (residues 159-165). Digestion of ovalbumin by chymotrypsin yielded the antimicrobial peptides AEERYPILPEYL (residues 127-138), GIIRN (residues 155-159) and TSSNVMEER (residues 268-276). The peptides were synthesized and found to exert antimicrobial activity. They were strongly active against Bacillus subtilis and to a lesser extent against the other bacterial strains examined. A weak fungicidal activity against Candida albicans was also shown by some peptides. Ovalbumin itself was not bactericidal against all the bacteria strains examined. Our results suggest that the food protein ovalbumin may supply the organism with antimicrobial peptides, supporting the immunodefences of the organism.

The antiviral activity of naturally occurring proteins and their peptide fragments after chemical modification

Chemical modification of the proteins bovine serum albumin, alpha-lactalbumin, beta-lactoglobulin and chicken lysozyme by 3-hydroxyphthalic anhydride (3-HP) yielded compounds which exerted antiviral activity in vitro as compared with the native unmodified proteins. Of the three enveloped viruses tested, human herpes simplex virus type 1 (HSV-1), bovine parainfluenza virus type 3 and porcine respiratory corona virus, only HSV-1 proved sensitive to the 3-HP-proteins. All of the chemically modified proteins presented antiviral activity against HSV-1 when assayed before, during or after infection. However, to achieve HSV-1 inhibition, significantly higher concentrations of the modified proteins were required if present before infection as compared to during or after infection. Our results suggest that multiple mechanisms are involved in the inhibition of HSV-1 infection. Proteolytical digestion of albumin, alpha-lactalbumin, beta-lactoglobulin and lysozyme by trypsin, chymotrypsin and pepsin yielded several peptide fragments with antiherpetic activity. Chemical modification of these peptide fragments by 3-HP generated peptides with antiviral activity, however, this was almost always combined with a cytotoxic effect on the Vero cells. Overall, our results suggest that targeted chemical modification of some natural products might provide compounds effective against HSV-1 infection.

Local expression of apolipoprotein A-I gene and a possible role for HDL in primary defence in the carp skin

Antimicrobial proteins and peptides play an important role in the primary defence of epithelial barriers in vertebrates and invertebrates. Here we report the detection of the apolipoproteins A-I and A-II in the epidermis and epidermal mucus of the carp (Cyprinus carpio L.) by immunohistochemistry and Western blot analysis. Both apolipoproteins are major constituents of high density lipoprotein and have been shown to display antiviral and antimicrobial activity in mammals. Therefore the aim of this study was to evaluate if they could be part of the innate immune system of teleost fish. A cDNA clone containing most of the coding region for carp apoA-I was isolated and used as a probe to demonstrate the expression of apoA-I gene in the skin. In addition, mucus apoA-I was shown to be associated to small particles that could correspond to nascent HDL. Finally, affinity purified plasma HDL displayed bactericidal activity in vitro against a non-pathogenic Escherichia coli strain, suggesting a defensive role for HDL and its associated proteins in the carp epidermis and mucus.