Upon exiting the endoplasmic reticulum and entering the Golgi apparatus via vesicular transport, a specific lysosomal tag, mannose 6-phosphate, is added to the peptides. The presence of these tags allows for binding to mannose 6-phosphate receptors in the Golgi apparatus, a phenomenon that is crucial for proper packaging into vesicles destined for the lysosomal system.
Upon leaving the Golgi apparatus, the lysosomal enzyme-filled vesicle fuses with a late endosome, a relatively acidic organelle with an approximate pH of 5.5. This acidic environment causes dissociation of the lysosomal enzymes from the mannose 6-phosphate receptors. The enzymes are packed into vesicles for further transport to established lysosomes. The late endosome itself can eventually mature into mature lysosomes, as evidenced by the transport of endosomal membrane components from the lysosomes back to the endosomes
