Catalyzes the oxidative deamination of D-amino acids. Has very broad substrate specificity; all the D-amino acids tested can be used as the substrate except D-Glu and D-Gln. Participates in the utilization of several D-amino acids as the sole source of nitrogen, i.e. D-alanine, D-histidine, D-phenylalanine, D-serine, D-threonine, and D-valine. A + a D-alpha-amino acid + H2O = a 2-oxocarboxylate + AH2 + NH4(+) kcat is 0.74 sec(-1) with D-alanine as substrate. kcat is 0.84 sec(-1) with D-histidine as substrate. kcat is 1.10 sec(-1) with D-phenylalanine as substrate. kcat is 1.10 sec(-1) with D-tyrosine as substrate. kcat is 0.97 sec(-1) with D-proline as substrate. kcat is 0.80 sec(-1) with D-serine as substrate. kcat is 0.68 sec(-1) with D-threonine as substrate. kcat is 0.78 sec(-1) with D-valine as substrate. kcat is 1.27 sec(-1) with D-arginine as substrate. Amino-acid degradation; D-alanine degradation; NH(3) and pyruvate from D-alanine: step 1/1. Is highly up-regulated by L- and D-alanine. However, it is likely that intracellular L-Ala is the signal for induction of the dadAX genes through DadR binding to several putative operator sites. Cells lacking this gene lose the ability to utilize D-alanine, D-histidine, D-phenylalanine, D-serine, D-threonine, and D-valine as the sole source of nitrogen. Belongs to the DadA oxidoreductase family. Was originally thought to be a heterodimer based on the purification of the enzyme first reported from E.coli B, but results of enzyme assays in PubMed:21378189 have indicated that DadA is solely responsible for the observed dehydrogenase activity.