Using differential solubility in 70% ethanol, the polypeptide components of the reduced and cyanoethylated glutenin from the prepared dough were fractionated into three fractions (AF-1, AF-2, and AF-3). In these fractions, AF-1 was identified as an aggregative subunit of glutenin from the results of SDS-PAGE. The sugar composition of carbohydrates in AF-1 was determined by gas chromatography, which revealed the presence of arabinose, xylose, and mannose as well as glucose and galactose. The presence of arabinose and xylose as a major sugar component in AF-1 suggested a significant role for pentosan (hemicellulose component) in aggregation. However, the differences between the sugar components of AF-1 fractionated from fermented and unfermented dough were almost negligible except for decreasing the amount of glucose.