Metabolism of 2-Ketoaldehydes in Bacteria: Oxidative Conversion of Methylglyoxal to Pyruvate by an Enzyme from Pseudomonas putida

Enzymes that catalyze the oxidation or reduction of methylglyoxal were screened for in several prokaryotic and eukaryotic microorganisms. Methylglyoxal-reducing activity was found to be widely distributed at considerably high levels in microorganisms. Methylglyoxal-oxidizing activity was detected only in cells of Pseudomonas putida among the organisms examined. The enzyme responsible for the methylglyoxal oxidation was purified approximately 240 fold from a cell extract of P. putida. The enzyme consisted of a single polypeptide chain with a molecular weight of 42,000 and showed a pH optimum of 8.0. The enzyme was active on 2-ketoaldehydes [glyoxal, methylglyoxal (Km = 1.0 mm) and phenylglyoxal] and some aldehydes (formaldehyde, acetaldehyde, glycolaldehyde and propionaldehyde) in the presence of NAD (^m = 0.1mm). The bacterial methylglyoxal-oxidizing enzyme appeared similar to goat liver 2-ketoaldehyde dehydrogenase in molecular weight and structure, but was different in its substrate affinity.