Malonic Acid Biosynthesis in Bush Bean Roots. II. Purification and Properties of Enzyme Catalyzing Oxidative Decarboxylation of Oxaloacetate

Abstract

An enzyme preparation from bush bean roots that catalyzes the oxidative decarboxylation of oxaloacetate to yield malonate was partially purified by heat and MnCl2 treatment, (NH4)2SO4 fractionation, and chromatography on a diethylaminoethyl-cellulose column. The enzyme requires manganous ions and an unidentified constituent present in boiled root extract. The enzyme is inhibited by azide. The pH optimum is approximately 5.4 and the reaction is essentially irreversible. Prior incubation of the enzyme with manganous ions and bioled root extract was shown to eliminate a time lag in malonate synthesis. Including a catalytic quantity of H2O2 in the reaction mixture substituted for the preincubation treatment. Stoichiometry studies showed the enzyme catalyzed tne following reaction: [image] It is suggested that the bean root enzyme understudy is a peroxidase enzyme that catalyzes the oxidation of oxaloacetate in a manner analogous to other peroxidase catalyzed oxidations. It is probable that the enzyme under study constitutes a major pathway in malonate biosynthesis in bush bean roots and perhaps other tissues.