Metabolism of 2-Oxoaldehydes in Bacteria: Purification and Characterization of Methylglyoxal Reductase from Escherichia coli

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The activities of 2-oxoaldehyde-metabolizing enzymes (glyoxalase I, glyoxalase II, methylglyoxal reductase, methylgjyoxal dehydrogenase and lactaldehyde dehydrogenase) were found to be widely distributed among microorganisms. One of the enzymes, methylglyoxal reductase, which catalyzes the reductive conversion of methylglyoxal into lactaldehyde, was purified from Escherichia coli cells. The enzyme was judged to be homogeneous on polyacrylamide gel electrophoresis and was a monomer with a molecular weight of 43000. The enzyme was most active at pH 6.5 and 45°C. The enzyme utilized both NADPH and NADH for the reduction of 2-oxoaldehydes (glyoxal, methylglyoxal, phenylglyoxal and 4, 5-dioxovalerate) and some aldehydes (glycolaldehyde, D, L-glyceraldehyde, propionaldehyde and acetaldehyde). The Km values of the enzyme for methylglyoxal, NADPH and NADH were 4.0mM, 1.7μM and 2.8 μM, respectively. The product of methylglyoxal reduction was identified as lactaldehyde. The enzyme from E. coli cells was different from the yeast and goat liver enzymes in both molecular structure and substrate specificity.
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