Abstract
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.