Catalyzes the alpha,beta-elimination reaction of both L- and D-alpha,beta-diaminopropionate (DAP) to form pyruvate and ammonia. In vitro L- and D-isomers of serine are also degraded, though slowly; it is the only serine dehydratase which can eliminate an amino group at the beta-carbon position. In vivo L-, D- and a mixure of DL-DAP allow growth. DL-DAP is toxic in the absence of this enzyme, it may inhibit enzymes involved in the synthesis of pyruvate and aspartate, as well as amino acids derived from them. (S)-2,3-diaminopropanoate + H(+) + H2O = 2 NH4(+) + pyruvate (R)-2,3-diaminopropanoate + H(+) + H2O = 2 NH4(+) + pyruvate Binds 1 pyridoxal phosphate per subunit. Competitively inhibited by L- and D-alanine. Optimum pH is 8.0. Homodimer. By DL-DAP (at protein level). No growth on minimal medium plus DL-DAP; growth can be restored by a mix of 8 amino acids (Arg, Asn, Cys, Glu, Ile, Leu, Met and Thr). Belongs to the diaminopropionate ammonia-lyase family.