Cereal Chem 47:331 - 344.  |  VIEW ARTICLE
Thermal Aggregation of Glycinin Subunits.

N. Catsimpoolas, S. K. Funk, and E. W. Meyer. Copyright 1970 by the American Association of Cereal Chemists, Inc. 

Glycinin, the major reserve globulin of soybean seeds (Glycine max) is dissociated into subunits by exposure to temperatures above 70 C. The thermal aggregation of these subunits was investigated by kinetic scattering absorbance measurements at 320 millimicrons. The rate and extent of aggregation were enhanced by low ionic strength and the presence of mercaptoethanol. The thermal aggregation of the subunits was depressed at extreme acidic or alkaline pH values, and by high ionic strength. Maximum rate of aggregation was obtained between pH 4.0 and 6.0. Involvement of ionic and hydrophobic bonds in the aggregation process was strongly suggested. Complete dissociation of the protein into subunits, by cleavage of disulfide bonds with mercaptoethanol, appeared to be one of the conditions favoring aggregation. Thermal aggregation which involves dissociation of glycinin into subunits could be distinguished from intermolecular aggregation of the protein at ambient temperatures as the result of pH adjustment of the region of the isoelectric point. These aggregates were dissolved by heat, and hence, disruption of hydrogen bonds was indicated.