Properties and Specific Functional Features of Wheat Grain α-Amylase/Subtilisin Inhibitor

Abstract

A protein bifunctional inhibitor of endogenous α-amylase and subtilisin has been isolated from wheat grain and purified. The inhibitor specifically inactivates α-amylase isozymes with high isoelectric point values (group α-AMY1) and has almost no effect on the α-AMY2 isozymes with low isoelectric point values. This enzyme does not belong to glycoproteins and has a molecular weight of 21 kDa and an isoelectric point of 7.2. The protein displays a relatively high thermostability and pH optimum of 8.0; its inhibitory activity requires the presence of Ca²⁺ cations. The inhibition of excess α-amylase in wheat grain with a low falling number by the purified protein is studied.