Wheat Flour Proteases and Their Action on Gluten Proteins in Dilute Acetic Acid

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Abstract
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 for the second highest molecular weight subunit of glutenin and for some other proteins.

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