Studies of the synthesis, structure and function of the phosphorylated oligosaccharides of lysosomal enzymes.
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Date
1983-12
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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 Nacetylglucosamine
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.
Description
Keywords
Lysosomal enzymes, I-cell disease, phosphorylated oligosaccharides
Citation
Varki Ajit P, Reitman Marc L, Tabas Ira, Kornfeld Stuart. Studies of the synthesis, structure and function of the phosphorylated oligosaccharides of lysosomal enzymes. Journal of Biosciences. 1983 Dec; 5(suppl_1): s101-s104.