Amino acids gliadin

Gliadins 35 Soluble in aqueous solutions of alcohol (e.g., 70% ethanol or 55% isopropanol) Primarily globular proteins (MW 30,000-40,000) stabilized by intramolecular disulfide bonds Rich in Glu, Pro, and hydrophobic amino acids, and low content of basic amino acids Glu and Asp in primarily amide form low net charge... 

H Wieser, A Modi, W Seilmeier, HD Belitz. High-performance liquid chromatography of gliadins from different wheat varieties amino acid composition and N-terminal amino acid sequence of components. Z Lebensm Unters Forsch 185 371-378, 1987. 

Kasarda, D.D., Autran, J.C., Lew, E.J.L., Nimmo, C.C., Shewry, P.R. 1983. N-terminal amino acid sequences of co-gliadins and co-secalins Implications for the evolution of prolamin genes. Biochim Biophys Acta 747 138-150. 

Picarelli, A., Di Tola, L., Sabbatella, M., Greco, L., Silano, R., De Vincenzi, M. 1999. 31 43 Amino acid sequence of the a-gliadin induces endomysial antibody production during in vitro challenge. Scand J Gastroenterol 34 1099-1102. 

These features of substrate specificity of tTG are mirrored by epitope specificity of gliadin antibodies of CD patients. The common core of the nona-peptides specifically recognized by antibodies of CD patients is QPEQPFP with the amino acid proline residing in position +2 [127]. However, in accordance with results from studies of substrate specificity of tTG [182], exchange of phenylalanine residue for tyrosine completely abolished binding of IgA of CD patients [127]. 

Studies of epitope specificity of gliadin antibodies and substrate specificity of tTG point to a role of proline and phenylalanine in amino acid positions +2 and +3 in glutamine deamidation. In contrast, investigations of T-cell stimulatory peptides reveal several potent T-cell stimulatory peptides from the N-terminal part of a-type gliadin containing the PELPY motif. In this connection, it was shown that substitution of phenylalanine in the +3 position or other amino acids in the glutenin peptide Git-156 inhibited the T-cell proliferative response [186]. 

Cornell HJ. Amino acid composition of peptides remaining after in vitro digestion of a gliadin sub-fraction with duodenal mucosa from patients with coeliac disease. Clin Chim... 

From the unique amino acid composition of the gliadin proteins, one would expect a structure that is quite different from globular proteins. However, optical rotation studies have shown that the gliadin proteins possess compact tertiary structures similar to those of globular proteins (4,5). 

Dietary protein sources differ widely in their proportions of the EAA. In general, complete proteins (those containing sufficient quantities of EAA) are of animal origin (e.g., meat, milk, and eggs). Plant proteins often lack one or more EAA. For example, gliadin (wheat protein) has insufficient amounts of lysine, and zein (com protein) is low in both lysine and tryptophan. Because plant proteins differ in their amino acid compositions, plant foods can provide a high-quality source of essential amino acids only if they are eaten in appropriate combinations. One such combination includes beans (low in methionine) and cereal grains (low in lysine). 

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