primary prevention of coeliac disease - Associazione Italiana ...

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76 GENETICALLY DETOXIFIED GRAINS molecular weight proteins. High-molecular weight proteins (x - and y-type subunits) comprise the HMW subunits of glutenins; glutamine, glycine, and proline represent 70% of total residues. Medium-molecular weight group consists of w-gliadins; 80% of the amino acids is due to glutamine, proline, and phenylalanine, but cysteine and methionine, i.e. sulphur containing amino acids, are almost absent. Low-molecular weight proteins consist of a-, b-, g-gliadins and LMW subunits of glutenins; they are rich in sulphur containing amino acids. Functional properties of gluten proteins Although the only known function of these proteins is to act as storage proteins, by releasing nitrogen for the germinating seed, their biochemistry structure has a crucial 2,6 role in providing the unique baking quality of wheat . Both LMW and HMW have not only intrachain but also interchain disulphide bonds allowing them to crosslink other glutenin and gliadin peptides, which results in the formation of beta-spirals. During the baking process, CO 2 is produced by yeast fermentation and is trapped in the beta-spiral three dimensional net. Glutenins spirals become extended but maintain the capacity to return to the colloid state. So, elasticity and cohesivity of the dough system are due to the cross-linked nature of the glutenin subunits, mainly the high molecular weight glutenins. On the other hand, soluble monomeric gliadins guarantee extensibility and viscosity to the dough (Fig. 1). Coeliac toxicity of gliadins and glutenins Since the demolition of these proteins to single amino acids results on loss of coeliac C C N N N TECHNOLOGICAL PROPERTIES N N C C C HMWx HMWy LMW g a Elasticity & Cohesivity Extensibility & Viscosity Fig. 1. Schematic representation of gluten protein components. Black segments unique sequence; white segments repeating sequence; ] intrachain disulphide bond; - interchain disulphide bond; C C-terminal sequence; N N-terminal sequence; HMWx high-molecular weight glutenins x-type subunit; HMWy high-molecular weight glutenins y-type subunit; LMW low-molecular weight glutenins; g-gliadins; a-gliadins.
GENETICALLY DETOXIFIED GRAINS 77 toxicity, several studies investigated which one of the several gluten components is responsible for CD intolerance. Briefly, a-, b-, g- and w-gliadins are all toxic for CD patients. Although glutenins were considered to be non dangerous for coeliac patients, 1,7 their safety is at least controversial . First of all alcohol extraction does not lead to clear-cut fractions. So, gliadins have actually been found within the insoluble glutenins, and that is an obstacle in understanding pure glutenin toxicity. Moreover, it has very recently been shown that glutenin peptides can induce an in-vitro specific activation and proliferation of T cell from coeliac small bowel. Such a response is virtually identical to that seen with gliadin peptides and is nowadays considered to be an indirect 8-9 evidence of coeliac toxicity . Although a major effort needs to be done to understand which gluten components are toxic in CD, this knowledge would be extremely important in order to develop genetically detoxified grains (GDG). The development of wheat strains lacking those genes coding for toxic peptides is hopefully regarded as a new and profitable tool for the treatment of CD. GDG could provide the solution to problems such as the poor palatability and high costs of commercially available gluten-free foods. GDG may be theoretically achieved with the modern techniques of genetic plant engineering which makes the deleting or silencing of one or more genes a possible approach. Genetics of wheat proteins Bread wheat is a hexaploid species containing three different but related genomas 10-11 (A, B, and D), each consisting of seven chromosome pairs (Fig. 2) . Information for storage proteins is encoded by clustered or dispersed gene families located on chromosomes 1 and 6 of the three different genomes. In particular, genes for a-gliadins are located on the short arm of chromosomes 6A, 6B, and 6D, tightly clustered at the Gli-A2, Gli-B2, and Gli-D2 loci. Genes coding for gw -and -gliadins are on the short arm 1A 1B 1D 6A Glu-1 (HMW) Glu-B2 Gli-A3 Gli-B3 Glu-3 (LMW) Gli-1 (gw) Gli-2 (ab) Gli-A5 Gli-B5 Gli-D5 6B 6D Long Arm Short Arm Fig. 2. Chromosomal position of the genes coding for storage proteins of bread wheat endosperm.
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Perspectives on Coeliac Disease Vol
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The AIC Meeting was held in the Aul
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Italian Coeliac Society, Via Picott
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Preface Coeliac disease (CD) is a u
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Contents Current understanding of t
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2 THE BASIS OF COELIAC DISEASE hapl
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4 THE BASIS OF COELIAC DISEASE 1 pr
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6 THE BASIS OF COELIAC DISEASE spre
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8 THE BASIS OF COELIAC DISEASE Ackn
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10 THE BASIS OF COELIAC DISEASE glu
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Catassi C, Fasano A, Corazza GR (ed
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T CELL RESPONSES TO GLUTEN PEPTIDES
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18 A DOMINANT EPITOPE IN GLUTEN PEP
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Page 40 and 41: 26 A DOMINANT EPITOPE IN GLUTEN PEP
Page 42 and 43: 28 ROLE OF A-GLIADIN 31-49 PEPTIDE
Page 45 and 46: Catassi C, Fasano A, Corazza GR (ed
Page 47 and 48: COELIAC DISEASE IN THE SAHARAWI 33
Page 55: COELIAC DISEASE IN THE SAHARAWI 41
Page 58 and 59: 44 INFANT FEEDING PRACTICES AND COE
Page 66 and 67: Age (years) 52 INFANT FEEDING PRACT
Page 76 and 77: 62 MECHANISMS OF ORAL TOLERANCE the
Page 78 and 79: 64 MECHANISMS OF ORAL TOLERANCE pot
Page 80 and 81: 66 MECHANISMS OF ORAL TOLERANCE Epi
Page 82 and 83: 68 MECHANISMS OF ORAL TOLERANCE typ
Page 84 and 85: 70 MECHANISMS OF ORAL TOLERANCE 51
Page 86 and 87: 72 MECHANISMS OF ORAL TOLERANCE 23.
Page 89: Catassi C, Fasano A, Corazza GR (ed
Page 93 and 94: • • GENETICALLY DETOXIFIED GRAI
Page 95 and 96: GENETICALLY DETOXIFIED GRAINS 81 3.
Page 99 and 100: IMMUNOTHERAPY OF COELIAC DISEASE 85
Page 101 and 102: IMMUNOTHERAPY OF COELIAC DISEASE 87
Page 105 and 106: RECENT ADVANCES ON GLUTEN TOXICITY
Page 107 and 108: Index A Antiendomysium antibodies (
Page 109: INDEX 95 W Wheat, 7, 23, 27, 31, 53
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