Barley Malt alpha-Glucosidase. IV. Studies on the Kinetics and the Active Groups.

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Abstract
The time course of the hydrolysis of maltose by an [alpha]-glucosidase from barley malt has been investigated to high degrees of reaction. It was found that the time course of the reaction for different initial concentrations of maltose, glucose and enzyme could be described by a chronometric integral consisting of a sum of a first-order and a zero-order term. A reaction mechanism based on the chronometric integral found is suggested. The influence of pH on the Michaelis constant Km and on the maximum velocity V suggests that two ionizable groups with pKa[image]4.0 and pKa[image]5.8 are involved in the mechanism of the enzymatic hydrolysis. The influence of sulfhydryl reagents, mercuric-chloride, phenylmercuric-acetate, iodoacetamide and N-ethylmaleimide has been examined; only mercuric-chloride and phenylmercuric-acetate showed inhibition.
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