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Gluten Proteins in Relation to Celiac Disease. Donald D. Kasarda, Ph.D. Research Chemist (Retired)/Collaborator U.S. Department of Agriculture Agricultural Research Service Western Regional Research Center Albany, California. Diagram of a Wheat Kernel. starch granule. endosperm protein.
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Gluten Proteins in Relation to Celiac Disease Donald D. Kasarda, Ph.D. Research Chemist (Retired)/Collaborator U.S. Department of Agriculture Agricultural Research Service Western Regional Research Center Albany, California
Diagram of a Wheat Kernel
starch granule endosperm protein FLOUR PARTICLES
Glutamine/Proline Composition of Wheat Prolamins (Mole Percent) Gln Pro Gln + Pro w gliadins 43-54 20-29 63-83 a, b, g gliadins + 36-42 15-19 51-61 LMW-glutenin subunits 12-27 42-55 30-38 HMW-glutenin subunits
“Consensus” Repeat Types for Gluten Proteins -P-Q-Q-P-(Y/F)-P a-gliadins -Q-Q-P-Q-Q-P-F-P- g-gliadins -Q-P-Q-Q-P-F-P- D-type w-gliadins B-type w-gliadins -Q-Q-Q-F-P- LMW-glutenin subunits -Q-Q-Q-Q-P-P-F-S- -Q-Q-G-Y-Y-P-T-S-P- HMW-glutenin subnits
Molecular model of a 13-residue gliadin peptide (a 13-mer) Tyr Pro Gln Gln Pro Gln Gln Pro Pro Gln Phe Gly Leu L-G-Q-Q-Q-P-F-P-P-Q-Q-P-Y
Currently Favored Analytical Method for Gluten in Food R-5 monoclonal antibody ELISA test is available commercially. Antibody reacts with monomeric wheat, rye, and barley prolamins, but not oat avenins; reacts weakly or not at all with glutelins (glutenin). Detection down to about 1.5 parts per million; quantification above 2.5 parts per million has been reported. RecognizesQQPFP and LQPFP motifs most strongly. The Codex Alimentarius Committee on Methods agreed in 2004 to endorse temporarily the R5 ELISA for the determination of gluten. Possible problems: failure to detect glutelin (glutenin) proteins and small peptides from hydrolysates.