Amino acid composition of gluten fractions

Abstract

Gluten dispersions in 10% sodium salicylate were fractionated by precipitation with increasing concentrations of magnesium sulfate. Dialysis of the dispersion against the dispersing agent to which sodium bisulfite had been added served merely to sharpen the separation of the fractions. Dialysis against the dispersing agent to which sodium sulfite had been added resulted in failure to recover much of the less soluble portion of the gluten by precipitation. It is suggested that the sulfite ruptured disulfide bonds of the less soluble fractions of gluten.The amino acid composition of successive fractions varied regularly, with the less soluble fractions containing less glutamic acid and proline and more arginine, lysine, aspartic acid, threonine, glycine, alanine, and tryptophan than did the more soluble fractions. This relationship among fractions was not altered by the exposure of gluten to reducing agents.Precipitates produced during hydrolysis of the gluten fractions by papain also varied regularly in amino acid composition but the proportions of individual amino acids were entirely different from those for the total protein in the fraction.Gluten must be considered as a complex combination of protein components but the number of components involved cannot yet be determined.