Purification and properties of lactaldehyde dehydrogenase from Escherichia coli.

An aldehyde dehydrogenase capable of acting on Llactaldehyde was detected in a strain of Escherichia coli K-12 selected to grow on 1,2-propanediol as the sole source of carbon and energy. This enzyme activity was purified over 200-fold by ammonium sulfate fractionation followed by diethylaminoethyl cellulose chromatography, Sephadex G-100 gel flltration, and DEAE-Sephadex chromatography. The purified enzyme appears different from the other known aldehyde dehydrogenases in that it specifically converts L-lactaldehyde to lactic acid. This enzyme uses NAD as coenzyme, has a high K, for L-lactaldehyde, and displays a broad pH optimum in the alkaline region. It is produced constitutively by the above bacterial mutant and is essential for the catabolism of 1,2-propanediol. Chemicals-DL-1,2-Propanediol, obtained from Fisher, was purified by dist,illation. L-Lactic acid was from Schwnrz BioResearch; methylglyox-al, propionaldehyde, acetnldehyde, Dand L-threonine, N:\D, RADII, NADP, pig heart lactic acid dehydrogenase, and glyo;ualase were from Sigma. nn-Glyccraldehyde was from Matheson Coleman and Bell; nucleotide analogues from P-L Biochemicals; acetol from K and Ii Laboratories; methyl indole from Distillation Products Industries; Sellhader G-100 and DEICE-Sephades A-50 from Pharmacia; DEAEcellulose (Whatman DE-52 microgranular) from W and It Balston, Ltd.; and AG l-X2 exchange resin from Bio-Rad. hcid hydrolysate of casein was purchased from Nutritional Biochemicals. lJ4C-u~-l ,2-Propanediol, of specific activity 48 &i per pmole, was obtained from International Chemical and Nuclear Corporation.