Catalyzes the sodium-dependent uptake of extracellular D-alanine and L-alanine (PubMed:15659675, PubMed:30659158). Can also transport glycine (PubMed:30659158). Binds glycine and both enantiomers of alanine, while strictly excluding other amino acids (PubMed:30659158). D-alanine(in) + Na(+)(in) = D-alanine(out) + Na(+)(out) L-alanine(in) + Na(+)(in) = L-alanine(out) + Na(+)(out) glycine(in) + Na(+)(in) = glycine(out) + Na(+)(out) Maintains pseudo twofold symmetry even though it contains an uneven number of transmembrane domains. No growth on L- or D-alanine. Belongs to the alanine or glycine:cation symporter (AGCS) (TC 2.A.25) family.