The function of SLC15A2 (solute carrier family 15 member 2, ENSG00000163406) is as follows. Proton-coupled amino-acid transporter that transports oligopeptides of 2 to 4 amino acids with a preference for dipeptides (PubMed:16434549, PubMed:18367661, PubMed:7756356). Transports neutral and anionic dipeptides with a proton to peptide stoichiometry of 2:1 or 3:1 (By similarity). In kidney, involved in the absorption of circulating di- and tripeptides from the glomerular filtrate (PubMed:7756356). Can also transport beta-lactam antibiotics, such as the aminocephalosporin cefadroxil, and other antiviral and anticancer drugs (PubMed:16434549). Transports the dipeptide-like aminopeptidase inhibitor bestatin (By similarity). Also able to transport carnosine (PubMed:31073693). Involved in innate immunity by promoting the detection of microbial pathogens by NOD-like receptors (NLRs) (By similarity). Mediates transport of bacterial peptidoglycans across the plasma membrane or, in macrophages, the phagosome membrane: catalyzes the transport of certain bacterial peptidoglycans, such as muramyl dipeptide (MDP), the NOD2 ligand (PubMed:20406817). {ECO:0000250|UniProtKB:P46029, ECO:0000250|UniProtKB:Q63424, ECO:0000250|UniProtKB:Q9ES07, ECO:0000269|PubMed:16434549, ECO:0000269|PubMed:18367661, ECO:0000269|PubMed:20406817, ECO:0000269|PubMed:31073693, ECO:0000269|PubMed:7756356}.