Involved in phosphonate degradation. (2-aminoethyl)phosphonate + pyruvate = L-alanine + phosphonoacetaldehyde Thr-243 of one partner binds the pyridoxal phosphate moiety of the other. Optimum pH is 6.5-9.5 for phosphonoacetaldehyde formation, and 7.5-8.5 for 2-aminoethyl phosphonate formation. Homodimer. Induced when inorganic phosphate is limiting; this is controlled by PhoB. Maps to a phosphate-starvation-inducible locus previously known as psiC. Belongs to the class-V pyridoxal-phosphate-dependent aminotransferase family. PhnW subfamily. The crystal structure does not show the Schiff base that is expected to form between Lys-194 and the pyridoxal phosphate cofactor.