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:11390972, PubMed:12598615). May be involved in the efflux from the lysosomal compartment of neutral amino acids resulting from proteolysis (PubMed:12598615). May play a role in specifying sites for exocytosis in neurons (PubMed:12598615). glycine(in) + H(+)(in) = glycine(out) + H(+)(out) H(+)(out) + L-proline(out) = H(+)(in) + L-proline(in) D-proline(out) + H(+)(out) = D-proline(in) + H(+)(in) H(+)(in) + L-alanine(in) = H(+)(out) + L-alanine(out) D-alanine(in) + H(+)(in) = D-alanine(out) + H(+)(out) H(+)(in) + L-serine(in) = H(+)(out) + L-serine(out) D-serine(out) + H(+)(out) = D-serine(in) + H(+)(in) 4-aminobutanoate(in) + H(+)(in) = 4-aminobutanoate(out) + H(+)(out) beta-alanine(in) + H(+)(in) = beta-alanine(out) + H(+)(out) In neurons, colocalizes with the exocyst complex in the axonal processes. Widely expressed and predominantly expressed in brain. Within the brain, expression restricted to neurons and not detected in glial cells. Abundant in regions rich in neurons using glutamate and GABA such as Purkinje cells in the cerebellum and pyramidal cells in the hippocampus. Belongs to the amino acid/polyamine transporter 2 family.