Novel carboxylated N-glycans contain oligosaccharide-linked glutamic acid

Biochem Biophys Res Commun. 2005 Jul 15;332(4):1020-7. doi: 10.1016/j.bbrc.2005.05.056.


We previously reported that N-glycans from bovine lung contain novel carboxylate groups. Here, we provide evidence that the carboxylated glycans contain glutamic acid. We labeled HeLa cells with [2,3-(3)H]glutamate and used a carboxylate-specific monoclonal antibody to enrich for the desired proteins. PNGaseF digestion of these proteins released labeled N-glycans with a free amino group and 1-3 carboxylates. Mild acid hydrolysis had no effect, but strong acid hydrolysis of the glycans released >80% of the (3)H as glutamate. Reducing the carboxylates to alcohols prior to hydrolysis eliminated the [(3)H]glutamate and generated [(3)H]4-amino 5-hydroxy pentanoic acid, suggesting that [(3)H]glutamate was linked to the glycan through its gamma-carboxyl. The glutamate-containing N-glycans resisted exoglycosidase digestion and oligosaccharide processing inhibitors greatly reduced [(3)H]glutamate incorporation. These results demonstrate that mammalian cells synthesize complex-type N-glycans with glutamate linked to their antennae, further expanding their potential for covalent or ionic interactions.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acids / pharmacology
  • Amino Acids / pharmacology
  • Carboxylic Acids / metabolism
  • Chromatography
  • Chromatography, High Pressure Liquid
  • Concanavalin A / pharmacology
  • Escherichia coli / metabolism
  • Flow Cytometry
  • Glutamic Acid / chemistry*
  • HeLa Cells
  • Humans
  • Hydrocarbons, Iodinated / chemistry
  • Hydrolysis
  • Immunoprecipitation
  • Ions
  • Oligosaccharides / chemistry*
  • Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase / pharmacology
  • Polysaccharides / chemistry*
  • Xanthomonas / metabolism


  • Acids
  • Amino Acids
  • Carboxylic Acids
  • Hydrocarbons, Iodinated
  • Ions
  • Oligosaccharides
  • Polysaccharides
  • Concanavalin A
  • Glutamic Acid
  • 2-amino-5-hydroxyvaleric acid
  • methyl iodide
  • Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase