SEPARATION AND PURIFICATION OF RICE ORYZENIN SUBUNITS BY ANION-EXCHANGE AND GEL-PERMEATION CHROMATOGRAPHY

Rice storage protein (oryzenin) was separated in three main subunits (33, 22, and 14 kDa). The low molecular weight (14 kDa) subunit, although it was related immunologically to rice prolamins, was an integral part of oryzenin because it could not be separated from oryzenin (or from rice flour) by H2O, 5% NaCl, or diluted ethyl or propyl alcohols. The oryzenin subunits were at first partially purified on DEAE Sepharose CL-6B and then further purified on Sephacryl S-200. All three main subunits contained strongly bound glucose or polysaccharide chains based on glucose. Isoelectric focusing of the 33-kDa purified subunit resulted in nine acid spots within the pH range 5-8. Isoelectric focusing of the 22-kDa purified subunit resulted in five basic spots within the pH range 8-11. Isoelectric focusing of the 14-kDa subunit resulted in three basic spots with pH 8.7, 8.8, and 9.0.