The creation of the M6P marker in the Golgi relies on recognition of a signal patch in the tertiary structure of the hydrolase.
		Patients with a disease called inclusion-cell disease have cells lacking hydrolases in their lysosomes.  Instead, the hydrolases are found in the blood.  These patients lack GlcNAc phophotransferase.  Without the M6P- tag, the acid hydrolases are transported to the plasma membrane instead of the late endosome.