Gliadin is the major seed storage protein in wheat. Expressed in endosperm. Substrate of transglutaminase. Causes an allergic reaction in human. Is the cause of the celiac disease, also known as celiac sprue or gluten-sensitive enteropathy. An internal 33-mer peptide seems to be the primary initiator of the inflammatory response to gluten in Celiac Sprue patients. The alpha/beta-gliadins can be divided into 5 homology classes. Sequence divergence between the classes is due to single base substitutions and to duplications or deletions within or near direct repeats. There are more than a 100 copies of the gene for alpha/beta-gliadin per haploid genome. Belongs to the gliadin/glutenin family.