Improvement of the Nutritional Value of Soybean [Glycine max (L) Merr.] Seed with Alteration in Protein Subunits of Glycinin (11S Globulin) and β-conglycinin (7S Globulin)

Protein quality in soybean seeds is strongly influenced by nutritional conditions. Glycinin (11S globulin) and β-conglycinin (7S globulin) are the 2 main proteins in soybean seeds. Protein quality of glycinin (11S) is higher than that of β-conglycinin (7S), due to the presence of higher amounts of s-containing amino acids (methionine and cysteine) in glycinin than β-conglycinin. Of the amino acids in glycinin, 3%-4.5% are methionine and cysteine but these important amino acids are not found in β-conglycinin (especially β-subunit). Pot studies were conducted with soybean [Glycine max (L) Merr.] grown under various levels of KCl and CaHPO4 and the effects of salts (fertilizers) on glycinin and β-conglycinin subunits were evaluated. Abundance of glycinin subunits (high quality) and β-conglycinin (poor quality) was determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDSPAGE). Quantitative changes in total protein (cytosolic protein) were determined by the Lowry test. Some significant differences were recognized between the measured factors and various treatments. The highest amount of total protein (%) and acidic subunit of glycinin containing more methionine and cysteine was observed in seeds of plants grown in the soil treated with 30 g of KCl and 0.02 g of CaHPO4 per 100 kg of soil. A lower amount of protein was observed when no fertilizer (0 P and 0 K) was applied in the growth medium. The current study showed that improvement of soybean nutritional value can be achieved by increasing the content of 11S proteins and decreasing 7S proteins.