Arginine decarboxylase from a Pseudomonas species

Abstract

An arginine decarboxylase has been isolated from a Pseudomonas species. The enzyme is constitutive and did not appear to be repressed by a variety of carbon sources. After an approximately 40 fold purification, the enzyme appeared more similar in its properties to the Escherichia coli biosynthetic arginine decarboxylase than to the E. coli inducible (biodegradative) enzyme. The Pseudomonas arginine decarboxylase exhibited a pH optimum of 8.1 and an absolute requirement of Mg2+ and pyridoxal phosphate, and was inhibited significantly at lower Mg2+ concentrations by polyamines putrescine, spermidine, and cadaverine. The K(m) for L arginine was about 0.25 mM at pH 8.1 and 7.2. The enzyme was completely inhibited by p chloromercuribenzoate. The inhibition was prevented by dithiothreitol, a feature that suggests the involvement of an SH group. Of a variety of labeled amino acids tested, only L arginine, but not D arginine, was decarboxylated. D Arginine was a potent inhibitor of arginine decarboxylase with a K(i) of 3.2 μM.