1-3 PPD dehydrogenase (EC 1.1.1.202) was purified to homogeneity from Clostridium butyricum E5 grown anaerobically on glycerol in continuous culture. The native enzyme was estimated by gel filtration to have a molecular weight of 384 200 +/- 31 100 Da; it is predicted to exist as an octamer or a decamer of identical molecular weight subunits. When rested as a dehydrogenase, the enzyme was most active with 1-3 propane diol. In the physiological direction, 3-hydroxypropionaldehyde was the preferred substrate. The apparent K-m values of the enzyme for 3-hydroxypropionaldehyde and NADH were 0.17 mM and 0.06 mM, respectively. The enzyme requires only Mn2+ for full activity. The enzyme was found to have properties similar to those reported for Klebsellia pneumoniae, Citrobacter freundii, and Clostridium pasteurianum.