Functions as a sodium-dependent amino acid transporter which countertransport protons. Mediates the saturable, pH-sensitive, and electrogenic cotransport of several neutral amino acids including glycine, asparagine, alanine, serine, glutamine and histidine with sodium. Not inhibited by lithium. Predominantly expressed in stomach, brain, liver, lung and intestinal tract. Belongs to the amino acid/polyamine transporter 2 family.