Abstract
Targetting of newly synthesized lysosomal enzymes to lysosomes requires mannose 6-phosphate receptors. These receptors shuttle between the Golgi apparatus, an organelle of the secretory route, and acidic prelysosomal organelles, which are part of the endocytic route. Vectorial transport of the ligands is ensured by the pH dependence of ligand binding. Ligands are bound at near-neutral pH in the Golgi apparatus and released in the acidic prelysosomal organelles.