Cereal Chem 58:325 - 330.  |  VIEW ARTICLE
New Aspects of Subunit Structure of Soybean Glycinin.

R. B. Iyengar and P. Ravestein. Copyright 1981 by the American Association of Cereal Chemists, Inc. 

Glycinin, the most important storage protein from soybean, was isolated from an aqueous extract of defatted soymeal by cryoprecipitation and hydroxyapatite chromatography. After complete reduction and alkylation, four different acidic subunits were isolated by ion-exchange chromatography in the presence of urea. No attempt was made to isolate the basic subunits, which were treated as a group. Following partial reduction and alkylation three different intermediary subunits, each consisting of one acidic and one basic subunit held together by one or more disulfide bridges, were isolated. The fractions were characterized by polyacrylamide gel electrophoresis in urea, dansyl chloride for N-terminal analysis, and sodium dodecyl sulfate polyacrylamide gel electrophoresis for relative molecular mass determinations. Peptide mapping after tryptic hydrolysis, amino-acid analyses, and automated sequence analyses of the first 20-30 residues of the acidic subunits demonstrated a close similarity in their primary structures. In the preparation of the intermediary subunits, the presence of a "free" subunit identical to an acidic subunit was repeatedly observed. Glycinin appears to consist of two identical half molecules, each consisting of three intermediary subunits, and two additional acidic subunits that probably occupy the central hole of each half molecule.