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The substrate specificity of the enzyme endo-alpha-N-acetyl-D-galactosaminidase from Diplococcus pneumonia

M M Brooks1, A V Savage

  • 1Department of Chemistry, University College, Galway, Ireland.

Glycoconjugate Journal
|February 1, 1997
PubMed

Insights

Endo-alpha-N-acetyl-D-galactosaminidase specifically cleaves the Gal beta1-3GalNAc glycan. This enzyme does not release sialylated trisaccharides or the major GlcNAc beta1-3GalNAc structure from tested substrates.

Area of Science:

  • Biochemistry
  • Glycobiology
  • Enzymology

Background:

  • Endo-alpha-N-acetyl-D-galactosaminidase plays a role in the O-linked glycosylation pathway.
  • Understanding its substrate specificity is crucial for interpreting glycosylation patterns.

Purpose of the Study:

  • To re-examine the substrate specificity of endo-alpha-N-acetyl-D-galactosaminidase from Diplococcus pneumonia.
  • To clarify enzyme activity on newly described core types and sialylated substrates.

Main Methods:

  • Incubation of the enzyme with desialylated bovine submaxillary mucin.
  • Incubation with remodelled antifreeze glycoprotein containing specific sialylated trisaccharides.
  • Analysis of released glycan structures using radiolabeling.

Main Results:

  • The enzyme exclusively released the minor Gal beta1-3GalNAc disaccharide from desialylated bovine submaxillary mucin.
  • The major GlcNAc beta1-3GalNAc disaccharide and other structures were not released.
  • No sialic acid-containing trisaccharides were released from the remodelled antifreeze glycoprotein substrates.

Conclusions:

  • Endo-alpha-N-acetyl-D-galactosaminidase exhibits strict specificity for the Gal beta1-3GalNAc core.
  • The enzyme does not act on sialylated O-linked glycans or the GlcNAc beta1-3GalNAc structure.
  • These findings resolve ambiguities regarding the enzyme's activity on various glycan structures.

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