In vitro mucosal digestion of synthetic gliadin-derived peptides in celiac disease

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Abstract
Two celiac-active synthetic peptides derived from the A-gliadin structure corresponding to residues 8–19 (LQPQNPSQQQPQ) and to 11–19 were digestedin vitro with small intestinal mucosa from children with celiac disease in remission and from normal children. The products of digestion were separated into two fractions on the basis of Mr400 by gel permeation chromatography and subjected to amino acid analysis. After digestion of the dodecapeptide with celiac mucosa, 71±14% (molar) of the total digestion products remained in the Mr>400 fraction. Glutamine, proline, serine, and asparagine were the major amino acids present. Glutamine, proline, and leucine were the major amino acids in the Mr400 fraction from the celiac mucosal digestion of the nonapeptide was of similar composition to the corresponding fraction from the dodecapeptide and represented 78±15% of the total products. Digestion of the two peptides with normal mucosa gave lower amounts of products in the Mr>400 fraction, but they were of similar composition to the corresponding fractions from the celiac mucosal digestion. Peptides such as NPSQQQP and QNPSQQQ may be present in the Mr>400 fractions since glutamine and proline are present in the approximate ratio of 2∶1, respectively. The results indicate a defect in the mucosal digestion of peptides which are active in an animal model of celiac disease.