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    • Keywords


      Lysosomal enzymes; I-cell disease; phosphorylated oligosaccharides; glycoproteins

    • Abstract


      Newly synthesized lysosomal enzymes were found to contain N-acetylglucosamine residues in phosphodiester linkage to the 6 position of the mannose residues on high-mannose type oligosaccharides. The formation of these structures was shown to be catalyzed by a specific N-acetylglucosaminylphosphotransferase enzyme, that utilises UDP-N-acetylglucosamine as a donor. The phosphorylation reaction can take place on any of four or five positions on the high-mannose oligosaccharide. Subsequently an α-N-acetylglucosaminylphosphodiesterase removes the outer blocking N-acetylglucosamine residues to generate the mature phosphomannsoyl recognition signal. This signal is responsible for the targetting of newly synthesized lysosomal enzymes to lysosomes. The human syndromes of I-cell disease (Mucolipidosis II) and pseudo-Hurler polydystrophy (Mucolipidosis III) were shown to be caused by deficiency of the first enzyme in the pathway, the UDP-N-acetylglucosamine: Glycoprotein N-acetylglucosaminylphosphotransferase.

    • Author Affiliations


      Ajit P Varki1 2 Marc L Reitman1 Ira Tabas1 Stuart Kornfeld1

      1. Department of Internal Medicine and Biological Chemistry, Washington University School of Medicine, St. Louis, Missouri - 63130, USA
      2. The Cancer Center, University of California at San Diego, San Diego, California - 92093, USA
    • Dates

  • Journal of Biosciences | News

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      Posted on July 25, 2019

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