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At least 613 records · Page 34Linked to original sources
PubMed1998

Specificity of a wheat gluten aspartic proteinase.

The substrate and peptide bond specificities of a purified wheat gluten aspartic proteinase (GlAP) are studied. GlAP shows maximum gluten hydrolysing activity at pH 3.0. At this pH, especially the wheat high molecular weight glutenin subunits (HMW-GS) and to a lesser extent the low molecular weight glutenin subunits and gliadins are hydrolysed. GlAP has no obvious effect on albumins and globulins. In its action on oxidised insulin B-chain, GlAP forms eight peptides and has high specificity for peptide bonds located between amino acid residues with large hydrophobic side chains (Leu, Phe, Tyr) but the peptide bond Glu13-Ala14 is also hydrolysed. Although structurally quite similar to a barley aspartic proteinase, the peptide bond specificity of GlAP towards oxidised insulin B-chain resembles slightly more that of a cardoon aspartic proteinase, cardosin B. HMW-GS 7, purified from cultivar Galahad-77, is rapidly hydrolysed by GlAP. N-Terminal amino acid sequence data show that GlAP cleaves at least one Met-Ile peptide bond at the end of the N-terminal domain and two Val-Leu peptide bonds in the repetitive domain of HMW-GS 7.

Albumins↗
PubMed1999

In vitro screening of food peptides toxic for coeliac and other gluten-sensitive patients: a review.

Experience gained through investigations on coeliac disease makes it possible to propose a screening method based on agglutination of isolated K562(S) cells to evaluate the occurrence in food protein of amino acid sequences that are able to adversely affect coeliac and related gluten-sensitive patients. The method consists of in vitro sequential peptic and tryptic digestion of food protein fractions under optimal pH, temperature and time conditions and in vitro incubation of the digest with K562(S) cells; the toxic potential is detected as an agglutination of K 562 (S) cells after a short incubation. Other in vitro test systems, including atrophic coeliac intestinal mucosa and rat fetal intestine, can be used to confirm the results obtained with the isolated cells. A fractionation step of the proteolytic digest on a sepharose-mannan column before exposure of the in vitro systems to the separated peptide fractions adds to the sensitivity of the method. This screening method is not only very useful to investigate action mechanisms in coeliac disease, but also to assess the safety of genetically-modified plant foods and novel foods for gluten-sensitive patients.

Amino Acid Sequence↗
PubMed2003

Intravenous administration of the food-derived opioid peptide gluten exorphin B5 stimulates prolactin secretion in rats.

Gluten Exorphin B5 (GE-B5) is a food-derived opioid peptide, identified in vitro in enzymatic digests of wheat gluten. It has been suggested that this peptide may play a regulatory role on pituitary secretion, since it stimulates prolactin (PRL) secretion when administered in the cerebral ventricles in rats. It is not known, however, if GE-B5 can exert this stimulatory action after peripheral administration. In order to clarify this aspect, we gave the following treatments to four groups of male rats: intravenous (i.v.) vehicle, GE-B5 3 mg/kg body weight i.v., naloxone intraperitoneally (i.p.) followed by vehicle i.v., naloxone i.p. followed by GE-B5 i.v. Blood samples for PRL were taken at intervals for 60 min after vehicle or GE-B5 administration. At the dose of 3 mg/kg body weight, GE-B5 induced a significant increase in PRL levels; naloxone completely abolished any effect of GE-B5 on PRL secretion. The present study indicates that GE-B5 stimulates PRL secretion after peripheral administration and that its action is mediated via classical opioid receptors; moreover, it identifies the minimum peptide dose which must reach the blood in order to exert its action on PRL secretion.

Animals↗
PubMed2003

Design, synthesis, and evaluation of gluten peptide analogs as selective inhibitors of human tissue transglutaminase.

Recent studies have implicated a crucial role for tissue transglutaminase (TG2) in the pathogenesis of Celiac Sprue, a disorder of the small intestine triggered in genetically susceptible individuals by dietary exposure to gluten. Proteolytically stable peptide inhibitors of human TG2 were designed containing acivicin or alternatively 6-diazo-5-oxo-norleucine (DON) as warheads. In biochemical and cell-based assays, the best of these inhibitors, Ac-PQP-(DON)-LPF-NH(2), was considerably more potent and selective than other TG2 inhibitors reported to date. Selective pharmacological inhibition of extracellular TG2 should be useful in exploring the mechanistic implications of TG2-catalyzed modification of dietary gluten, a phenomenon of considerable relevance in Celiac Sprue.

Animals↗
PubMed2006

Effects of temperature and water content on the secondary structure of wheat gluten studied by FTIR spectroscopy.

The effect of temperature on gluten conditioned at the following water contents, 0%, 13%, and 47% (wet weight basis), was studied by FTIR spectroscopy over the temperature range of 25-85 degrees C. A detailed discussion of the assignment of the amide I band is given. At 0% hydration no changes in the secondary structure with temperature could be detected; spectra were consistent with a tight disordered structure with many protein-protein interactions. At 13% hydration, distinctive changes occurred in the low-frequency region of the amide I band (1,630-1,613 cm(-1)). This was attributed to changes in the beta-sheet structure. On cooling to 25 degrees C, these changes were mainly reversed. It was noted that most of the changes observed occurred above the glass transition temperature. At 47% hydration, more complex changes took place: as the temperature was raised distinct bands at 1,630 and 1,613 cm(-1) merged. However, this process was partially reversed, with recovery of both bands, on cooling. The significance of these results in relation to other changes in gluten proteins in flour and dough with temperature and water content is discussed.

Glutens↗
PubMed2006

Enlarged processing window of plasticized wheat gluten using salicylic acid.

The temperature window for the extrusion of glycerol-plasticized wheat gluten was increased by the use of salicylic acid, a known scorch retarder and radical scavenger. It was possible to extrude 30 wt % glycerol-wheat gluten films with a die-head temperature as high as 135 degrees C, rather than 95 degrees C, by incorporating only 1 wt % salicylic acid. Small effects of shear-induced heating during extrusion at the higher temperatures suggested that the acid acted as a lubricant and viscosity reducer. The latter was suggested to originate primarily from the salicylic-acid-induced reduction in the degree of protein aggregation/cross-linking, as indicated by size-exclusion high-performance liquid chromatography and chemiluminescence. Electron paramagnetic resonance spectroscopy on extruded films indicated that the beneficial effect of salicylic acid was due to its radical scavenging effect. Tensile tests on extrudates revealed that the materials produced at the substantially higher processing temperature were still ductile. The complex shear modulus increased more slowly with increasing salicylic acid content above 110-120 degrees C, indicating that the aggregation/cross-linking rate was slower with salicylic acid, that is, that it did have a scorch-retarding effect, besides yielding a lower final degree/complexity of aggregation.

Chromatography, High Pressure Liquid↗
PubMed2001

Low-temperature brewing by freeze-dried immobilized cells on gluten pellets.

A biocatalyst, prepared by the immobilization of a cryotolerant strain of Saccharomyces cerevisiae on gluten pellets, was freeze-dried without any protecting medium and used for repeated batch fermentations of wort for each of the temperatures 15, 10, 5, and 0 degrees C. The fermentation time for freeze-dried immobilized cells was about 2-fold that of the corresponding time for wet immobilized cells on gluten pellets, and lower than the corresponding time for freeze-dried free cells, especially at 5 and 0 degrees C. Beers produced by freeze-dried immobilized cells contained alcohol levels in the range of 5.0-5.5% v/v, diacetyl concentrations lower than 0.5 mg/L, polyphenol concentrations lower than 145.5 mg/L, and free cell concentrations lower than 3 g/L. As a result, they had a very good clarity after the end of primary fermentation. The amounts of amyl alcohols were lower than 129.1 mg/L and reduced as the temperature was decreased. Ethyl acetate concentrations were found in the range of 22.1-29.2 mg/L, giving a very good aroma and taste in the produced beers.

Alcohols↗
PubMed2002

Analysis of taste-active compounds in an enzymatic hydrolysate of deamidated wheat gluten.

Hydrolyzed plant proteins are widely used as ingredients in culinary products for their glutamate-like ("umami") taste. Three hydrolysates were prepared from wheat gluten using different enzymatic approaches. Comparison of their taste profiles revealed the enzymatic hydrolysate of an acid-deamidated wheat gluten (WGH-3) to be the least bitter of all and to elicit an intense glutamate-like taste. Its umami taste intensity was similar to that of an enzymatic hydrolysate in which glutaminase had been employed to convert free glutamine to glutamic acid and which had a 3-fold higher concentration of free glutamate. Reconstitution studies based on the results of the chemical analysis of WGH-3 and sensory comparison of the model solution and WGH-3 indicated that other components in addition to glutamate and organic acids contribute to its glutamate-like taste. WGH-3 was fractionated by gel permeation chromatography and reversed phase high-performance liquid chromatography, and two fractions with a pronounced glutamate-like taste were obtained. In one of them four pyroglutamyl peptides were tentatively identified: pGlu-Pro-Ser, pGlu-Pro, pGlu-Pro-Glu, and pGlu-Pro-Gln. Apparently, these peptides were formed by cyclization of the N-terminal glutamine residues during the preparation of the hydrolysates.

Adult↗
PubMed2005

Influence of mycotoxin producing fungi (Fusarium, Aspergillus, Penicillium) on gluten proteins during suboptimal storage of wheat after harvest and competitive interactions between field and storage fungi.

Cereals contaminated by Aspergillus spp., Penicillium spp., and Fusarium spp. and their mycotoxins, for example, ochratoxin A (OTA) and deoxynivalenol (DON), are not only a risk to human and animal health but can also show poor technological properties and baking quality. The influence of these genera on the sulfur speciation of low molecular weight (LMW) subunits of glutenin was characterized by investigating suboptimally stored wheat samples in situ by X-ray absorption near edge structure (XANES) spectroscopy and baking tests. Field fungi of the genus Fusarium have hardly any influence on both the sulfur speciation of wheat gluten proteins and the baking properties, whereas storage fungi of the genera Aspergillus and Penicillium have a direct influence. An increased amount of sulfur in sulfonic acid state was found, which is not available for thiol/disulfide exchange reactions in the gluten network, and thus leads to a considerably reduced baking volume. From changes of the composition of the mould flora during suboptimal storage of wheat and from the mycotoxin contents, it can be concluded that microbial competitive interactions play an important role in the development of the mould flora and the mycotoxin concentrations during (suboptimal) storage of wheat.

Aspergillus↗
PubMed2006

Properties of aged montmorillonite-wheat gluten composite films.

The properties of new and aged glycerol-plasticized vital wheat gluten films containing < or =4.5 wt % natural or quaternary ammonium salt modified montmorillonite clay were investigated. The films were cast from pH 4 or pH 11 ethanol/water solutions. The films, aged for < or =120 days, were characterized by tensile testing, X-ray diffraction, and transmission electron microscopy. In addition, water vapor permeability (11% relative humidity) and the content of volatile components were measured. The large reduction in the water vapor permeability with respect to the pristine polymer suggests that the clay platelets were evenly distributed within the films and oriented preferably with the platelet long axis parallel to the film surface. The film prepared from pH 11 solution containing natural clay was, as revealed by transmission electron microscopy and X-ray diffraction, almost completely exfoliated. This film was consequently also the strongest, the stiffest, and the most brittle and, together with the pH 11 film containing modified clay, it also showed the greatest decrease in water vapor permeability. The large blocking effect of the clay had no effect on the aging kinetics of the films. During aging, the pH 4 and pH 11 film strength and the pH 4 film stiffness increased and the pH 4 film ductility decreased at the same rate with or without clay. This suggests that the aging was not diffusion rate limited, that is, that the loss of volatile components or the migration of glycerol or glycerol/wheat gluten phase separation was not limited by diffusion kinetics. The aging rate seemed to be determined by slow structural changes, possibly involving protein denaturation and aggregation processes.

Bentonite↗
PubMed2000

A bioelectrode for penicillin detection based on gluten-membrane-entrapped microbial cells.

A bioelectrode for penicillin detection was established using gluten membrane in which cells of Escherichia coli harbouring the plasmid pUC18 coding for penicillinase synthesis were entrapped. For the entrapment preparation, lyophilized cells were mixed with gluten solution during the formation of gel, and the resultant gel was hardened by the addition of oxidized starch. The immobilization procedure employed an inexpensive base material and avoided the use of purified enzyme. When the membrane with a thickness of 30 microm and a cell content of 33% (w/w) was used, the steady response of the bioelectrode to increasing concentrations of penicillin G buffered with 0.025 M phosphate was linear over the range of 1-16 mM. The response time was less than 3 min. Decreasing the cell content decreased the steady response due to a decline in enzymic activity. The treatment of lyophilized cells with ultrasonication or chemically with either N-cetyl-N,N,N-trimethylammonium bromide or guanidine hydrochloride rendered cells permeabilized and exposed the periplasmic enzyme to penicillin. The response time became shorter, but a serious decline in steady responses was observed because of the loss of enzyme activity during the cell permeabilization. The microbial electrode also showed different responses to penicillin G solution, depending on the pH and buffer concentration.

Buffers↗
PubMed1976

Functional and biochemical evidence of damage to enterocytes induced by triparanol: role of lysosomes and the effect of gluten-free diet.

1. Functional and biochemical studies were performed on the small intestine of control rats, and the results were compared with similar studies on animals given triparanol at a dosage of 0.114 mmol/kg daily for 10 days. The animals given triparanol were fed with either standard rat food or a gluten-free diet. 2. By using a recirculating-perfusion technique in vivo, it was shown that absorption of galactose from an 8 mmol/l solution was impaired in the ileum but not in the jejunum of the triparanol-treated rats. 3. Assays of marker enzymes for the principal subcellular organelles were performed on isolated jejunal and ileal enterocytes. In the ileum there was a striking decrease in lysosomal enzyme activities and a smaller but significant decrease of lactate dehydrogenase, catalase and malate dehydrogenase activities. In the jejunum there was no significant change in the activities of these enzymes. 4. Measurements of lysosomal integrity indicated that ileal lysosomal fragility was markedly increased and that jejunal lysosomes were affected to a much smaller extent. 5. These effects of triparanol could not be ameliorated by feeding with a gluten-free diet.

Acetylglucosaminidase↗
PubMed1998

Binding of gluten-derived peptides to the HLA-DQ2 (alpha1*0501, beta1*0201) molecule, assessed in a cellular assay.

The nature of the immunopathogenic relationship underlying the very strong association of coeliac disease (CD) to the HLA-DQ (A1*0501, B1*0201) genotype is not known, but probably relates to binding of gluten-derived epitopes to the HLA-DQ (alpha1*0501, beta1*0201) heterodimer (DQ2). These epitopes have not yet been defined. In this study we have tested the binding of various gluten-derived peptides to DQ2 in a cellular assay using Epstein-Barr virus (EBV)-transformed B lymphocytes and murine fibroblast transfectants. One of these peptides (peptide A), which has previously been shown to exacerbate the CD lesion in vitro and in vivo, was found to bind to DQ2, albeit only moderately, lending further credence to its possible role in the pathogenesis of CD. The nature of peptide A's binding to DQ2 was explored with truncated and conservative point substituted analogues and compared with the published DQ2 binding motif, the results of which explain the observed level of binding.

Amino Acid Sequence↗
PubMed2002

Gluten and casein free diets in autism: a study of the effects on food choice and nutrition.

BACKGROUND: There is growing interest in possible dietary involvement in the aetiology and treatment of Autistic Spectrum Disorders (ASD). Research has focused on the physiological and behavioural effects of dietary change but has not examined the effect of exclusion diets on nutritional intake. AIMS: The aim of this study was to examine whether the removal of major dietary staples placed children with autism at risk of nutrient deficiency and compares their food choice with ASD children not following gluten and/or casein free diets. METHODS: A postal questionnaire was sent to parents of children aged 3-16 years, diagnosed with ASD belonging to the National Autistic Society in Leicestershire and southern Derbyshire. Detailed dietary information and a 3-day food diary were collected. The sample size was small: those using gluten/casein free diets (n = 8) and those not following diet (n = 29). RESULTS: Nutrient intakes fell below the Lower Reference Nutrient Intake (LRNI) in 12 children (32%) for zinc, calcium, iron, vitamin A, vitamin B12 and riboflavin in the nondiet group and four children (50%) for zinc and calcium in the diet group. Fruit and vegetable intakes were higher and cereal, bread and potato consumption were lower in those children using gluten and/or casein free diets. CONCLUSION: No significant differences in the energy, protein and micronutrient intakes were found between the two groups of children. A longitudinal prospective study is suggested to examine whether differences in food choice are the result of dietary intervention or the prerequisite for the successful application of diet in this special group of children.

Adolescent↗
PubMed1997

Schizophrenic symptoms and SPECT abnormalities in a coeliac patient: regression after a gluten-free diet.

A 33-year-old patient, with pre-existing diagnosis of 'schizophrenic' disorder, came to our observation for severe diarrhoea and weight loss. Use of single photon emission computed tomography, (99mTc)HMPAO SPECT, demonstrated hypoperfusion of the left frontal brain area, without evidence of structural cerebral abnormalities. Jejunal biopsy showed villous atrophy. Antiendomysial antibodies were present. A gluten-free diet was started, resulting in a disappearence of psychiatric symptoms, and normalization of histological duodenal findings and of (99mTc)HMPAO SPECT pattern. This is the first case in which, in an undiagnosed and untreated coeliac patient with psychiatric manifestations, the (99mTc)HMPAO SPECT demonstrated a dysfunction of frontal cortex disappearing after a gluten-free diet.

Adult↗
PubMed1999

Duration of exposure to gluten and risk for autoimmune disorders in patients with celiac disease. SIGEP Study Group for Autoimmune Disorders in Celiac Disease.

BACKGROUND & AIMS: The relationship between celiac disease and many autoimmune disorders has been explained by the sharing of a common genetic factor. In a multicenter national study, we examined the relationship between the prevalence of autoimmune disorders in celiac disease and the duration of exposure to gluten. METHODS: Over a 6-month period, 909 patients with celiac disease (group A; mean age, 16.1 +/- 3.8 years; grouped according to age at diagnosis into three subgroups [group A1, <2 years; group A2, 2-10 years; and group A3, >10 years]), 1268 healthy controls (group B; mean age, 20.8 +/- 4.5 years), and 163 patients with Crohn's disease (group C; mean age, 28.8 +/- 10 years) were evaluated for the presence of autoimmune disorders. RESULTS: Prevalence of autoimmune disorders in group A was significantly higher than in group B (14% vs. 2.8%; P < 0.000001) but not higher than in group C (12.9%). Prevalence of autoimmune disorders in celiac disease increased with increasing age at diagnosis: 5.1% in group A1, 17% in group A2, and 23.6% in group A3 (P = 0.000001). In group A3, the prevalence of autoimmune disorders was significantly higher than in group C. In a logistic regression model, age at diagnosis was the only significant predictor variable of the odds of developing an autoimmune disorder (r = 0.3; P < 0.000001). CONCLUSIONS: Our data show for the first time that the prevalence of autoimmune disorders in celiac disease is related to the duration of exposure to gluten.

Adolescent↗
PubMed2006

Altered osteoprotegerin/RANKL ratio and low bone mineral density in celiac patients on long-term treatment with gluten-free diet.

Skeletal demineralization and mineral metabolism derangement are well-recognized features of untreated celiac disease (CD). Although treatment with a gluten-free diet appears to prevent bone loss while correcting skeletal demineralization in childhood, there is evidence that bone mineral density does not return to normal in celiacs diagnosed in adulthood. Osteoprotegerin (OPG), a member of the tumor necrosis factor receptor family, and ligand of receptor activator of NFkB (RANKL) are involved in the process of bone turnover and have been implicated in the pathogenesis of osteoporosis and other metabolic bone diseases. We measured OPG, RANKL, bone mineral density (BMD), and biochemical markers of bone turnover in 32 adult female premenopausal celiac patients on a gluten-free diet, and thirty age-matched healthy women. We correlated the OPG/RANKL ratio with the severity of bone loss. Celiac patients had a mean BMD lower than controls in lumbar spine and in the femoral neck. Serum levels of bone alkaline phosphatase (BAP, marker of bone formation), and urinary excretion of telopeptides of type I collagen (a marker of bone resorption) were significantly higher than in controls. Serum OPG and RANKL levels were significantly higher in CD patients than in controls, while the OPG/RANKL ratio was significantly lower in CD patients than in controls and was positively correlated with BMD at the spine. The role of elevated OPG in CD patients is unclear, but it might represent a compensatory mechanism against other factors that promote bone damage. Further studies are required to assess a possible therapeutic potential of osteoprotegerin in optimally treated celiacs with persistent osteopenia.

Adult↗
PubMed2000

Gluten-dependent diabetes-related and thyroid-related autoantibodies in patients with celiac disease.

Patients with celiac disease are at high risk of having autoimmune disorders. Moreover, untreated patients with celiac disease have been found to have a higher than expected prevalence of organ-specific autoantibodies. In a prospective study of 90 patients with celiac disease, we found that the prevalence of diabetes and thyroid-related serum antibodies was 11.1% and 14.4%, respectively. Like antiendomysium autoantibodies, these organ-specific antibodies seem to be gluten-dependent and tend to disappear during a gluten-free diet.

Case-Control Studies↗