Phosphorylated oligosaccharides in lysosomal enzymes: identification of alpha-N-acetylglucosamine(1)phospho(6)mannose diester groups.
In human fibroblasts, the recognition of lysosomal enzymes by cell surface receptors is mediated by mannose 6-phosphate residues located on oligosaccharides that can be cleaved by endo-beta-N-acetylglucosaminidase H. About half of these oligosaccharides, as isolated from beta-hexosaminidase and cathepsin D secreted by human skin fibroblasts, are anionic. Most of these are resistant to alkaline phosphatase. The resistance is due to alpha-N-acetylglucosamine residues linked to mannose 6-phosphate by a phosphodiester bond. The major phosphorylated oligosaccharides contain one and two and possibly three phosphate groups blocked by N-acetylglucosamine. Besides the blocked phosphate groups these oligosaccharides contain a common inner core consisting of Man alpha 1,6-(Man alpha 1,3)Man alpha 1,6(Man alpha 1,3)Man beta GlcNAc and either one or two alpha 1,2-linked mannose residues.
D000117:Acetylglucosamine / Q000032:analysis; D000469:Alkaline Phosphatase / Q000378:metabolism; D002403:Cathepsins / Q000032:analysis*; D006023:Glycoproteins / Q000032:analysis*; D006596:Hexosaminidases / Q000032:analysis*; D006801:Humans; D008247:Lysosomes / Q000201:enzymology*; D008360:Mannosephosphates / Q000032:analysis; D009844:Oligosaccharides / Q000032:analysis*; D010766:Phosphorylation
D006023:Glycoproteins; D008360:Mannosephosphates; D009844:Oligosaccharides; D000469:Alkaline Phosphatase; D006596:Hexosaminidases; D002403:Cathepsins; D000117:Acetylglucosamine