Degradation of Soybean Protein by an Acid Proteinase from Monascus anka

Degradation of soybean protein by Monascus-proteinase was investigated in order to reveal the role of the enzyme in the process of tofuyo ripening. The ratio of trichloroacetic acid-insoluble nitrogen of soybean protein to the total nitrogen in the reaction mixture decreased with increasing enzymatic reaction time. It was found that the digestion of soybean protein by this enzyme progressed as follows: initially, α'-, α-, and β-subunits in β-conglycinin, and then, the acidic subunit in glycinin were degraded. However, the basic subunit of glycinin still remained, and some polypeptide bands (around 10 kDa) were formed during the enzyme reaction. The degradation rate of soybean protein by this enzyme was affected by the ethyl alcohol concentration in the reaction mixtures.