Examination of the Structure of the Glutenin Macropolymer in Wheat Flour and Doughs by Stepwise Reduction

Abstract

The structure of the disulfide-bonded glutenin macropolymer (GMP) in flour and dough was studied by analyzing the depolymerization behavior during stepwise chemical reduction. During reduction, the size distribution of GMP changed, due to the release of subunits, dimers, and oligomers as well as small glutenin aggregates. Glutenin subunits were released from the polymer in a nonrandom order, which was indicative of the polymer having a hierarchical structural organization. Typically, the B-mobility low molecular weight glutenin subunits (LMW-GS) were released at lower reductant concentration than C-mobility LMW-GS and high molecular weight glutenin subunits (HMW-GS), although the B-subunits were released in a partially reduced state. Dimers comprised of either LMW- or HMW-GS were released at low reductant concentrations, but LMW- and HMW-GS were not found together in the same dimers. Some HMW-GS were particularly resistant to reductive dissociation, consistent with them forming a backbone to the glutenin macropolymer. Antibodies specific for different LMW-GS N-terminal sequence families were used to demonstrate that different families were released at different reductant concentrations. Only some of the sequence families were associated with LMW dimers. Individual subunits and dimers more readily depolymerized from overmixed doughs compared with flours. These studies suggest that the glutenin macropolymer in flours has a well-ordered structure that can be modified by dough mixing. Keywords: Flour; dough; protein; glutenin; disulfide; reduction