Cereal Chem 62:340-345 | VIEW
Involvement of Carbohydrates and Lipids in Aggregation of Glutenin Proteins.
U. Zawistowska, F. Bekes, and W. Bushuk. Copyright 1985 by the American Association of Cereal Chemists, Inc.
Glutenins were prepared from untreated flour, from flour partially defatted by eta-butanol and then by eta- hexane, and from flour totally defatted by water-saturated eta-butanol. The three glutenins differed in lipid contents, but all contained similar amounts of carbohydrate that upon hydrolysis yielded almost entirely glucose. Glutenins were then reduced and alkylated and fractionated on Sephadex G-200. Of the resulting three fractions, fraction I, which eluted at the void volume, had unusually high, for gluten, contents of lysine and aspartic acid, lower contents of glutamic acid and proline, and contained all the carbohydrate and lipid originally present in the glutenin. Sodium dodecyl sulfate electrophoresis showed that fraction I contained subunits of lower molecular weight than expected from their elution volumes, indicating aggregation. Fractions II and III were characteristic of gluten proteins rich in glutamic acid and proline. They contained no carbohydrate or lipid. After partial or total defatting, the proportion of fraction I changed, indicating that lipid contributed to the aggregation of the proteins in this fraction. Removal of carbohydrate from fraction I by digestion with amyloglucosidase produced further disaggregation. Sodium dodecyl sulfate electrophoresis of subfractions of fraction I from which the carbohydrate had been removed showed that they contained the same glutenin subunits as in the original fraction I but in different proportions. We concluded that the strong aggregative tendency of fraction I proteins of glutenin is determined mainly by protein structure, but specific lipids and carbohydrates contribute significantly to this behavior.