Purification and properties of L-Aspartate-alpha-decarboxylase, an enzyme that catalyzes the formation of beta-alanine in Escherichia coli

Abstract

L-Aspartate-alpha-decarboxylase, an enzyme that catalyzes the production of beta-alanine, has been purified to apparent homogeneity from Escherichia coli. The properties of the enzyme are: (a) pH optimum of 6.8 to 7.5, (b) temperature optimum of 55 degrees C, (c) Km for L-aspartate of 0.16 mM, and (d) molecular weight of 58,000. The activity of the enzyme is inhibited by reagents (hydroxylamine, phenylhydrazine, and sodium borohydride) that react with carbonyl groups, but no pyridoxal phosphate is present. The compound containing the carbonyl group has been identified as covalently bound pyruvate. Approximately 1 mol of pyruvate was found/mol of enzyme. That the enzyme has a biosynthetic function rather than a catabolic role is indicated by the observations that a mutant (designated as E. coli 99-2) which requires either beta-alanine or pantothenic acid for growth contains only trace amounts of enzyme activity, whereas it is present in substantial amounts in the parent strain (E. coli W) and in a spontaneous revertant of the mutant.