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Processing of lysosomal hydrolases in a healthy cell

In a healthy person, cells phosphorylate lysosomal hydrolases by GlcNAc-1-phosphotransferase in the cis-Golgi network. The uncovering enzyme removed the masking of N-acetylglucosamine (GlcNAc) to expose mannose 6-phosphate (M6P) residues in the trans-Golgi network (Velho RV, Harms FL, Danyukova T, et al. The lysosomal storage disorders mucolipidosis type II, type III alpha/beta, and type III gamma: update on GNPTAB and GNPTG mutations. Hum Mutat 2019;40(7):842-64.)
The M6P-exposed enzymes are taken up by endosomes with the M6P receptor and are delivered to lysosomes. (Source: Khan SA, Tomatsu SC. Mucolipidoses overview: past, present, and future. Int J Mol Sci 2020;21[18]:6812. Adapted from: Velho RV, Harms FL, Danyukova T, et al. The lysosomal storage disorders mucolipidosis type II, type III alpha/beta, and type III gamma: update on GNPTAB and GNPTG mutations. Hum Mutat 2019;40[7]:842-64. Creative Commons Attribution [CC BY] license. http://creativecommons.org/licenses/by/4.0.)