High affinity transporter for glutathione. Also transports tetra- and pentapeptides like the opioids leucine enkephalin (Tyr-Gly-Gly-Phe-Leu) and methionine enkephalin (Tyr-Gly-Gly_Phe-Met) across the cell membrane. Optimum pH is 5.5. Present with 2870 molecules/cell in log phase SD medium. Belongs to the oligopeptide OPT transporter family.