Comparative investigations of gluten proteins from different wheat species. III. N-terminal amino acid sequences of α-gliadins potentially toxic for coeliac patients

Abstract.

Studies on the coeliac toxicity of wheat have been focused on common (bread) wheat. Other cultivated wheat species were tested in an inadequate manner or were tested not at all. Because in vivo testing by feeding to coeliac patients is out of the question for ethical reasons, the different species were compared by N-terminal sequences of α-gliadins including the potential toxic sequences. Flours of durum wheat, emmer, and einkorn were successively extracted with a salt solution and 60% ethanol. The alcoholic extracts (gliadins) were preparatively separated by reversed-phase HPLC using an elution system optimized for α-gliadins. Five to six different α-gliadin fractions were isolated from each species and were characterized by the determination of N-terminal amino acid sequences. The results for 30 steps of Edman degradation indicated a high degree of sequence homology within the N-terminal region and a close relationship with corresponding sequences of α-gliadin fractions from bread wheat and spelt wheat [12]. The α-gliadins from all wheat species investigated contained amino acid sequences potentially activating coeliac disease. For this reason, all cultivated wheat species are assumed to be coeliac toxic cereals and should be avoided by coeliac patients.