Sodium-dependent amino acid/proton antiporter. Mediates electrogenic cotransport of glutamine and sodium ions in exchange for protons. Also recognizes histidine, asparagine and alanine. May mediate amino acid transport in either direction under physiological conditions. May play a role in nitrogen metabolism and synaptic transmission. Expressed predominantly in liver, moderately expressed in kidney and brain, and barely detectable in heart and muscle. Within liver, expressed in hepatocytes. Not detected in testis. Belongs to the amino acid/polyamine transporter 2 family.