A SERINE-PROTEASE IN SOYBEAN SEEDS THAT ACTS SPECIFICALLY ON THE NATIVE ALPHA-SUBUNIT OF BETA-CONGLYCININ

A proteolytic activity directed against the alpha subunit of beta-cong lycinin was detected in resting mature seeds of the soybean [Glycine m ax (L.) Merrill] cultivar Keburi. The relationship between pH and acti vity and the effect of protease inhibitors revealed that the enzyme wa s a neutral/alkaline serine protease. The proteolysis of the alpha sub unit of beta-conglycinin yielded a specific product with a molecular w eight of about 47,000, as determined by SDS-PAGE, but the enzyme had n o activity against the beta subunit. The amino acid composition, the m olecular weight and the amino-terminal amino acid sequence of the prot eolytic product revealed that the action of the enzyme on the alpha su bunit was specific, with cleavage occurring only at the R126-R127 pept ide bond of the alpha subunit. These characteristics of the protease i ndicate that the enzyme is a novel protease that has not previously be en recognized in soybean seeds.