The M6P-tagged lysosomal enzymes are shipped to the late endosomes via vesicular transport.Enzyme replacement therapy (ERT) for several lysosomal storage diseases relies on this pathway to efficiently direct synthetic enzymes to the lysosome where each can metabolize its particular substrate. The pH in the late endosome can reach 6.0, which causes dissociation of M6P from its receptor. Upon release, the enzymes are ferried to their final destination in the lysosomes. The MPRs are packed into vesicles that bud off the late endosome and return to the "trans"-Golgi network. In this way, the MPRs can be recycled.