Catalyzes the reversible reductive amination of pyruvate to L-alanine. Prefers L-alanine for oxidative deamination, other substrates are poorly reactive. In the other direction 2-oxobutyrate is almost as reactive as pyruvate. Ammonia is the sole amino donor for the reductive amination of pyruvate, NADPH is inert. Reductive amination proceeds through a sequential, ordered ternary-binary mechanism, where NADH binds first followed by ammonia and pyruvate; the products are released in the order L-alanine and NAD(+) (PubMed:488097, PubMed:2340274). A key factor in the assimilation of L-alanine as an energy source via the tricarboxylic acid cycle during sporulation (By similarity). H2O + L-alanine + NAD(+) = H(+) + NADH + NH4(+) + pyruvate Inhibited by p-chloromercuribenzoate and HgCl(2) and by Cu(2+) and Pb(2+) salts, unaffected by amino acids such as D-alanine and beta-alanine or by nucleotides or nucleosides. Optimum pH is 10.0-10.5 for the oxidative deamination of L-alanine and about 9.0 for reductive amination of pyruvate. Loses about 50% of its initial activity when heated at 65 degrees Celsius for 5 min. Amino-acid degradation; L-alanine degradation via dehydrogenase pathway; NH(3) and pyruvate from L-alanine: step 1/1. Homohexamer. Belongs to the AlaDH/PNT family.