Purification and Characterization of a New NAD⁺-Dependent Enzyme, L-Tartrate Decarboxylase, from Pseudomonas sp. Group Ve-2

Abstract

A new enzyme, L-tartrate decarboxylase, was found in cells of Pseudomonas sp. group Ve-2. The enzyme was purified to homogeneity and characterized. The enzyme requires K⁺, Mg²⁺, and NAD⁺ for L-tartrate decarboxylation. The dependence of the enzymatic decarbox-ylation on NAD⁺ suggests that the decarboxylation involves redox reactions of the sub-strate. The enzyme catalyzes NAD⁺-linked oxidative decarboxylation of D-malate as well. The enzyme is composed of four subunits with identical molecular weight (M_r 40, 000). The apparent Michaelis constants for L-tartrate and NAD⁺ are 7.0 and 1.1 mM, respectively. The cofactor requirements and the physical properties of the enzyme were similar to those of L-tartrate dehydrogenase-D-malate dehydrogenase from Rhodopseudomanas sphaeroides, and tartrate dehydrogenase from P. putida.