Controlled enzymatic hydrolysis of glycinin: Susceptibility of acidic and basic subunits to proteolytic enzymes

Glycinin, the major storage protein of soyabeans was enzymatically modified using papain, alcalase and fungal protease. The degree of hydrolysis (DH) was monitored by using trinitrobenzene sulphonic acid reaction with liberated α-amino groups. The DH could be varied by varying the ratio of enzyme to substrate, time and temperature of hydrolysis. The measured Km and Vmax values of glycinin with different proteases suggested that the susceptibility for hydrolytic cleavage of glycinin followed the order fungal protease>alcalase>papain. Electrophoretic analysis of cleaved glycinin suggested that acidic subunits of glycinin were cleaved preferentially over basic subunits. The measured Km and Vmax with acidic and basic subunits with fungal protease correlated with cleavage susceptibility. The functional properties of glycinin could be tailored by controlling the DH and using appropriate protease. Modified glycinin had better functional characteristics compared to glycinin.