SOYBEAN BASIC 7-S-GLOBULIN WHICH WAS DETECTED FROM OKARA AND ITS ISOLATION METHODS

Basic 7S globulin, an unique protein in soybean seed proteins, was det ected in the residue of soymilk production (Okara). A new preparation method of the protein from Okara was studied. Though the basic 7S glob ulin was not extracted with water, the protein was extracted with 0.3 M NaCl, denaturant (6. M urea or 0.1% sodium dodecyl sulfate) or a hig h pH solution, indicating that the protein associated with Okara throu gh non-covalent bonds. On the other hand, the basic 7S globulin was no t extracted even with the denaturants at 60-degrees-C or above. The tw o subunit bands (HMWS and LMWS) of the basic 7S globulin were observed in an extract with the denaturant containing 2-mercaptoethanol at 0.0 2 M or above even in this high temperature. After heating with a solut ion containing N-ethylmaleimide, an intermidiata subunit band (IS) of the protein was detected. These results indicated that the protein eas ily made crosslinks through disulfide bridge upon heating. The basic 7 S globulin extracted from Okara was purified on CM-Sepharose CL-6 B. T wo fraction (F 1 and F 2) obtained were 85 kDa and 42 kDa by HPLC. The electrophoretic patterns of the fraction, however, showed the same on SDS-urea electrophoresis, which suggested that the F 1 fraction conta ined the dimer and the F 2 fraction contained the monomer of the prote in. The yield was 2.2% of soybean seeds. This preparation method was b etter than the previous methods on the yield and reproducibility.