The precursors of lysosomal hydrolases are covalently modified by the addition of mannose 6-phosphate (M6P) groups in the cis Golgi network. They then become segregated from all other types of proteins in the trans Golgi network because adaptins in the clathrin coat bind the M6P receptors, which, in turn, bind the modified lysosomal hydrolases. The clathrin-coated vesicles produced bud off from the trans Golgi network and fuse with late endosomes. At the low pH of the late endosome, the hydrolases dissociate from the M6P receptors, and the empty receptors are recycled to the Golgi apparatus for further rounds of transport. It is not known which type of coat mediates vesicle budding in the M6P receptor recycling pathway. In the late endosomes, the phosphate is removed from the mannose sugars attached to the hydrolases, further ensuring that the hydrolases do not return to the Golgi apparatus with the receptor.