EXAMINATION OF THE STRUCTURE OF THE GLUTENIN MACROPOLYMER IN WHEAT-FLOUR AND DOUGHS BY STEPWISE REDUCTION

The structure of the disulfide-bonded glutenin macropolymer (GMP) in f lour and dough was studied by analyzing the depolymerization behavior during stepwise chemical reduction. During reduction, the size distrib ution of GMP changed, due to the release of subunits, dimers, and olig omers as well as small glutenin aggregates. Glutenin subunits were rel eased from the polymer in a nonrandom order, which was indicative of t he polymer having a hierarchical structural organization. Typically, t he B-mobility low molecular weight glutenin subunits (LMW-GS) were rel eased 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 w ere particularly resistant to reductive dissociation, consistent with them forming a backbone to the glutenin macropolymer. Antibodies speci fic for different LMW-GS N-terminal sequence families were used to dem onstrate that different families were released at different reductant concentrations. Only some of the sequence families were associated wit h LMW dimers. Individual subunits and dimers more readily depolymerize d from overmixed doughs compared with flours. These studies suggest th at the glutenin macropolymer in flours has a well-ordered structure th at can be modified by dough mixing.