Yukio Kawamura

Wheat flour proteases and their action on gluten proteins in dilute acetic acid.

The presence in wheat flour of several kinds of proteases was shown on the basis of pH-activity profile, substrate specificity, and response to inhibitors. Among them, 14C-hemoglobin and cbz-Phe-Ala hydrolases (14C-Hbase and CPAase) showed optimal activity around pH 4. 14C-Hbase was inhibited almost completely by pepstatin, and CPAase was partially inhibited by DFP. About 85% of 14C-Hbase activity and 40% of CPAase activity in the original flour were retained in gluten fraction. The decrease in viscosity of the gluten solution in dilute acetic acid was effectively prevented by pepstatin. An SDS-PAGE pattern showed that hydrolysis of gluten proteins was prevented effectively by pepstatin, although not completely, and that the simultaneous addition of pepstatin and DFP prevented completely self-digestion of the gluten proteins. Therefore, pepstatin and DFP sensitive proteases were shown to be responsible for the self-digestion of gluten proteins. The mode of action of these enzymes was relatively specific f...