Amino acid analyses of glutenins and gliadins

Abstract The amino acid compositions of glutenins and gliadins from two strong and two weak wheats have been compared. Glutenin appears to have an amino acid analysis generally similar to that of gliadin but there are individual differences. Glutenin possesses much higher proportions of lysine, glycine and tryptophan and somewhat higher proportions of arginine, tyrosine, threonine, (aspartic acid + asparagine), serine and alanine. Gliadin is richer in proline, (glutamic acid + glutamine), cystine, phenylalanine, amide nitrogen and isoleucine. No definite differences were observed in contents of methionine, valine, leucine or histidine. The possible significance of these results in explaining the properties of glutenin and gliadin is discussed, and the results are compared on a diagram with some analyses in the literature. No significant differences in amino acid composition from variety, or from strong wheats as against weak, were observed among glutenins or gliadins. The calculated factor for converting weight of nitrogen to glutenin or gliadin is 5.6. The mean percentage of (glutamic + aspartic) acids in the amide form is 82 for glutenin and 92 for gliadin.