Catalyzes the reversible oxidative deamination of L-alanine to pyruvate. Oxidative deamination proceeds through a sequential, ordered ternary-binary mechanism, where NAD(+) binds first followed by L-alanine; the products are released in the order ammonia, pyruvate and NADH (PubMed:6794611, PubMed:6794612) (Probable). Disruption blocks sporulation probably in stage V; 20-30% sporulation can be restored if the media is supplemented with pyruvate, suggesting lack of pyruvate blocks sporulation. Thus it is a key factor in the assimilation of L-alanine as an energy source via the tricarboxylic acid cycle during sporulation (PubMed:8226620). H2O + L-alanine + NAD(+) = H(+) + NADH + NH4(+) + pyruvate Amino-acid degradation; L-alanine degradation via dehydrogenase pathway; NH(3) and pyruvate from L-alanine: step 1/1. Homohexamer. Trimer of dimer (By similarity). A monocistronic operon. Induced by L-alanine in minimal media. Constitutively expressed in rich medium, declines during sporulation. Induced early during sporulation on minimal medium by L-alanine. Affects its own expression (PubMed:8226620). Transcription activated by AdeR (PubMed:22797752). Strain cannot grow on L-alanine as a sole carbon source. Disruption of ald causes a sporulation defect, most likely in stage V. Belongs to the AlaDH/PNT family.