CHANGES IN PEPTIDE SUBUNIT COMPOSITION OF ALBUMINS, GLOBULINS, PROLAMINS, AND ORYZENIN IN MATURING RICE GRAINS

Peptide subunit albumin, globulin, prolamin, and oryzenin (rice glutelin) preparations from preharvest maturing rice grains of U.S. Lemont (long grain) rice variety have been studied by SDS-PAGE. Relative quantitative composition of peptide subunits in albumin, globulin, prolamin, and oryzenin (rice glutelin) fractions changed significantly during maturing of rice grains. The results revealed that the synthesis of peptide subunits during maturing was uneven. The lower molecular weight subunits increased and the higher molecular weight subunits decreased between 14 and 50 days after flowering. This was especially apparent in the rice storage protein (oryzenin) fraction and resulted in a significantly lower average molecular weight of this fraction. The synthesis of intramolecular -SS- bonds was preferable to intermolecular -SS- bonds during this maturing period.