Catalyzes the reversible reductive amination of pyruvate to L-alanine. However, since the physiological environment of M.tuberculosis has a neutral pH, it can be assumed that the enzyme catalyzes exclusively the formation of L-alanine. May play a role in cell wall synthesis as L-alanine is an important constituent of the peptidoglycan layer. H2O + L-alanine + NAD(+) = H(+) + NADH + NH4(+) + pyruvate Binds 1 Mg(2+) ion per subunit. Inhibited by CuSO(4) and ZnCl(2). Optimum pH is between 10 and 11 for the oxidative deamination and between 7 and 7.5 for the reductive amination. Relatively stable, it loses only 25% of its total activity after 4 hours at 60 degrees Celsius. The enzyme is much more active at temperatures above 37 degrees Celsius, particularly in the reductive amination. The velocity almost doubles at temperatures between 60-65 degrees Celsius compared with 37 degrees Celsius. Above 65 degrees Celsius there is a sharp decrease in activity, due to thermal inactivation of the enzyme. Amino-acid degradation; L-alanine degradation via dehydrogenase pathway; NH(3) and pyruvate from L-alanine: step 1/1. Homohexamer. Trimer of dimers. Upon nutrient starvation. L-alanine dehydrogenase activity increases when the M.tuberculosis is shifted from aerobic to anaerobic growth conditions. Belongs to the AlaDH/PNT family.