Cereal Chem 57:415 - 420.  |  VIEW ARTICLE
Identity of High Molecular Weight Gliadin and Ethanol-Soluble Glutenin Subunits of Wheat: Relation to Gluten Structure.

J. A. Bietz and J. S. Wall. Copyright 1980 by the American Association of Cereal Chemists, Inc. 

The exact relationship, origin, and function of high molecular weight gliadin (HMWG) and ethanol-soluble reduced glutenin (ESRG), two heterogeneous wheat protein fractions, are not known. HMWG occurs as small oligomers, soluble in 70% ethanol, whereas ESRG is a disulfide-bonded fraction of glutenin, wheat's highest molecular weight protein class. Upon reduction and alkylation, both fractions are alcohol-soluble, consist of subunits having molecular weights near 44,000 and 36,000, and have similar electrophoretic and chromatographic properties and amino acid compositions. Amino-terminal sequence analyses now prove that many of the same polypeptides comprise HMWG and ESRG. Their N-terminal sequence distribution is H2N-(Val+Asn+Gln+Met)-(His+Gln+Met)-(Ile+Val)-(Pro+Val+Gln)-(Gly+Val+Gln+Asn)-(Leu+Pro)-Gln- (Leu+Gly)-(Pro+Gln+Leu)-(Gln+Pro+Val)-Gln-(Gln+Pro)-(Gln+Pro)-Pro-(Gln+Leu)-Pro-Gln-Gln-. These data imply that many of these polypeptides are homologous and that the heterogeneity of HMWG and ESRG results from duplication and mutation of a common ancestral gene. During biosynthesis, kernel maturation, or drying, these polypeptides can combine either with each other to form HMWG or with higher molecular weight ethanol-insoluble polypeptides and with highly aggregating polypeptides to form glutenin. A hypothesis explains how the ethanol-soluble nongliadin polypeptides with 44,000 and 36,000 mol wt contribute to gluten's structure and to dough's unique viscoelastic properties.