Cereal Chem 46:357 - 368.  |  VIEW ARTICLE
Separation of Soybean Whey Proteins by Isoelectric Focusing.

N. Catsimpoolas, C. Ekenstam, and E. W. Meyer. Copyright 1969 by the American Association of Cereal Chemists, Inc. 

Soybean whey proteins were separated by isoelectric focusing in the region between pH 3 and pH 10, and by high-resolution electrofocusing in the range of pH 3 to pH 6, and pH 5 to pH 8. The separated proteins exhibited a spectrum of isoelectric points (pI) ranging from pH 3.38 to pH 10. The separated fractions were analyzed by disc electrophoresis in 11% polyacrylamide gels. The protein components from the different fractions migrated in the alkaline gel (stacks at pH 8.9, runs at pH 9.5) in a stepwise fashion starting from the anodic end of the gel column and progressively approaching the cathode as the isoelectric point increases. Proteins which exhibited isoelectric points higher than 6.80 did not migrate in the alkaline gel. However, these components were resolved by electrophoresis in acidic gels (stacks at pH 5.0, runs at pH 4.3). Carrier ampholytes (used to form the pH gradient) could not be removed from a number of fractions by extensive dialysis against water. The presence of ampholytes was demonstrated by disc electrophoresis, since these are stained by amido schwartz dye. Several of the fractions were isolated in better than 95% purity in one-step electrofocusing. Preliminary results show that multiple trypsin inhibitors and hemagglutinins are present in the soybean, in agreement with previous reports. The various components exhibiting trypsin inhibitory activity can be separated more effectively by electrofocusing in the region of pH 3 to pH 6, and components exhibiting hemagglutinating activity, in the region of pH 5 and pH 8. Since the latter components are very antigenic, this property could be utilized for their identification.