Electrogenic proton-coupled amino-acid transporter that transports oligopeptides of 2 to 4 amino acids with a preference for dipeptides. Transports neutral and monovalently charged peptides with a proton to peptide stoichiometry of 1:1 or 2:1. Primarily responsible for the absorption of dietary di- and tripeptides from the small intestinal lumen. Mediates transepithelial transport of muramyl and N-formylated bacterial dipeptides contributing to recognition of pathogenic bacteria by the mucosal immune system 