J. Biol. Chem., Vol. 260, Issue 26, 13941-13946, Nov, 1985
Carbohydrates of lysosomal enzymes secreted by Tetrahymena pyriformis
T Taniguchi, T Mizuochi, Y Banno, Y Nozawa and A Kobata
The carbohydrate structures of acid phosphatase and alpha-glucosidase
secreted into culture medium by Tetrahymena pyriformis strain W were
studied. Their asparagine-linked sugar chains were quantitatively liberated
as radioactive oligosaccharides from their polypeptide moieties by
controlled hydrazinolysis followed by N-acetylation and NaB3H4 reduction.
The approximate amounts of total sugar chains liberated from 1 mol each of
acid phosphatase and alpha-glucosidase were 6 and 4 mol, respectively.
Paper electrophoresis revealed that only neutral oligosaccharides were
obtained from both enzymes. The oligosaccharide fraction from acid
phosphatase was separated into seven components by Bio-Gel P-4 column
chromatography while that from alpha- glucosidase was resolved into three
components. The structures of these oligosaccharides were determined by
sequential glycosidase digestion in combination with methylation analysis.
The sugar chains of the two enzymes can be primarily classified as high
mannose-type oligosaccharides. However, they have the following
characteristic features: 1) their common core is not the usual Man5 .
GlcNAc2 structure, it is Man3 . GlcNAc2; 2) some of the sugar chains of
acid phosphatase have 1 approximately 3 glucose residues linked to the
nonreducing terminal Man alpha 1----2 residue. The structural
characteristics of the sugar moieties of the two enzymes indicate that they
might be produced by the so-called "alternate pathway," in which
lipid-linked Glc3 . Man5 . GlcNAc2 functions as an oligosaccharide donor.
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