The pH 6 Acetolactate-forming Enzyme from Aerobacter aerogenes

Abstract

Abstract Kinetic studies have been performed with a recrystallized preparation of the pH 6 acetolactate-forming enzyme from Aerobacter aerogenes. The pH optimum in acetate is 5.8, and the enzyme activity is inhibited by phosphate and sulfate. These compounds cause sigmoidal kinetics, and apparent Michaelis kinetics is observed in acetate. The enzyme is sensitive to inhibition by the substrate analogues, glyoxylate and phenylpyruvate, and the inhibition is normal and strictly competitive in acetate. The activating effect of a number of acetate analogues has been tested, and acetate can be replaced by monochloroacetate, and to some extent by formate. Analogues with substitution in the carboxyl group had no activating effect, an indication that this group is essential for this effect. The possible biological significance of the regulation of the enzyme by acetate is discussed.