Involved in an anaerobic respiration pathway that converts the sulfonate taurine (2-aminoethanesulfonate) to ammonia, acetate and sulfide. Acts as an alanine dehydrogenase that regenerates pyruvate, the amino group acceptor for the taurine--pyruvate aminotransferase enzyme, and liberates ammonia. H2O + L-alanine + NAD(+) = H(+) + NADH + NH4(+) + pyruvate Organosulfur degradation; alkanesulfonate degradation. Homohexamer. Highly up-regulated in the presence of taurine. Taurine is an abundant dietary and host-derived molecule whose metabolism to hydrogen sulfide (H2S) by members of the human gut microbiota has many prominent connections to host health and disease. The human gut bacterium and opportunistic pathogen Bilophila wadsworthia produces H2S when respiring sulfite (HSO3-) released from organosulfonate substrates such as taurine and isethionate. Belongs to the AlaDH/PNT family.