Mode of inhibition of finger millet malt amylases by the millet phenolics

The effect of millet polyphenols on starch hydrolysis catalyzed by amylases developed during malting were investigated. The enzyme kinetic studies using Michaelis–Menten and Lineweaver–Burk equations showed the Km remained constant (0.625%) but the maximum velocity (Vmax) decreased in the presence of a crude extract of millet polyphenols, indicating mixed non-competitive inhibition. On the other hand, gallic acid, vanillic acid, quercetin and trans-cinnamic acid isolated from the polyphenol extract of the millet showed uncompetitive inhibition. Kinetic studies of amylase inhibition by phenolic compounds indicated the presence of secondary binding sites in malted finger millet amylases similar to other cereal amylases.