Studies on Trypsin Inhibitors in Japanese Soybeans

Abstract

The trypsin inhibitor patterns among thirteen varieties of Japanese soybeans were investigated by gel filtration and isoelectric forcusing. Water extractable protein in Japanese soybeans showed two protein peaks in gel filtration. The first peak did not show any inhibitor activity, but the second peak showed inhibitor activity. 4 to 6 inhibitors were isolated from the inhibitor peaks by isoelectric focusing. The isoelectric points of two major trypsin inhibitors were pH 4.20-4.25 and pH 4.45-4.55, respectively. Based on the difference of the inhibitor content, the 13 varieties of Japanese soybeans were divided into two groups.
It seems that the isolated trypsin inhibitor of pI 3.90-4.00 corresponds to 1.9S inhibitor, of pI 4.20-4.25 to Bowman-Birk inhibitor and of pI 4.45-4.55 to Kunitz inhibitor. The trypsin inhibitor of pI 3.70-3.80 was found in 3 varieties of Japanese soybeans. The pI 4.95-5.05 inhibitor isolated from 12 varieties of Japanese soybeans showed very low content. Trypsin inhibitor of pI 4.70-4.75 was first reported in the paper.