Isolation and Some Physico-chemical Properties of the Acidic Subunits of Soybean 11S Globulin

Four kinds of acidic subunits and three kinds of basic subunits of 11S globulin were separated by polyacryl amide gel electrophoresis in the urea system. The four acidic subunits designated as A₁, A₂, A₃ and A₄ (R_m=0.35, 0.40, 0.46 and 0.56 respectively) were isolated by stepwise elution followed by repeating gradient elution with DEAE-Sephadex A-50 in the presence of 6 m urea at 5°C.

Subsequently, some physico-chemical properties of the subunits were determined. For example, N-terminal amino acids were determined as phenylalanine for both A₁ and A₂ and as leucine (or isoleucine) for both A₃ and A₄ by the DNP-amino acid method. The molecular weights of A₁, A₂ and A₃ were shown as 37,000 and 45,000 for A₄ by SDS-gel electrophoresis. The amino acid compositions of the acidic subunits were roughly similar to each other, but some remarkable differences were observed in the content of basic amino acids (lysine, histidine and arginine), serine and proline.