Catalyzes the oxidative deamination of D-amino acids. Participates in the utilization of alanine as the sole source of carbon and nitrogen for growth. A + a D-alpha-amino acid + H2O = a 2-oxocarboxylate + AH2 + NH4(+) Amino-acid degradation; D-alanine degradation; NH(3) and pyruvate from D-alanine: step 1/1. By alanine; slightly repressed by glucose. Is activated by the Ntr system, mediated by the nitrogen assimilation control protein (NAC). Cells lacking this gene fail to use alanine as a carbon or nitrogen source and become sensitive to the presence of the amino acid in glucose-ammonium minimal medium. They exhibit a glutamate auxotrophy when ammonium is the sole source of nitrogen. Belongs to the DadA oxidoreductase family.