Electrogenic proton/amino acid symporter with selectivity for small apolar L-amino acids, their D-enantiomers and selected amino acid derivatives such as 4-aminobutanoate/GABA (PubMed:12809675, PubMed:12527723, PubMed:19549785). May be involved in the efflux from the lysosomal compartment of neutral amino acids resulting from proteolysis (By similarity). May play a role in specifying sites for exocytosis in neurons (By similarity). glycine(in) + H(+)(in) = glycine(out) + H(+)(out) H(+)(in) + L-alanine(in) = H(+)(out) + L-alanine(out) D-alanine(in) + H(+)(in) = D-alanine(out) + H(+)(out) H(+)(out) + L-proline(out) = H(+)(in) + L-proline(in) D-proline(out) + H(+)(out) = D-proline(in) + H(+)(in) D-serine(out) + H(+)(out) = D-serine(in) + H(+)(in) H(+)(in) + L-serine(in) = H(+)(out) + L-serine(out) 4-aminobutanoate(in) + H(+)(in) = 4-aminobutanoate(out) + H(+)(out) beta-alanine(in) + H(+)(in) = beta-alanine(out) + H(+)(out) Optimum pH is 5.0-5.5. In neurons, colocalizes with the exocyst complex in the axonal processes. Belongs to the amino acid/polyamine transporter 2 family. Aberrant splicing.