Artificial Cysteine S-Glycosylation Induced by Per-O-Acetylated Unnatural Monosaccharides during Metabolic Glycan Labeling

Angew Chem Int Ed Engl. 2018 Feb 12;57(7):1817-1820. doi: 10.1002/anie.201711710. Epub 2018 Jan 5.


The unexpected, non-enzymatic S-glycosylation of cysteine residues in various proteins by per-O-acetylated monosaccharides is described. This artificial S-glycosylation greatly compromises the specificity and validity of metabolic glycan labeling in living cells by per-O-acetylated azido and alkynyl sugars, which has been overlooked in the field for decades. It is demonstrated that the use of unacetylated unnatural sugars can avoid the artifact formation and a corrected list of O-GlcNAcylated proteins and O-GlcNAc sites in HeLa cells has been assembled by using N-azidoacetylgalactosamine (GalNAz).

Keywords: O-GlcNAc; S-glycosylation; chemoproteomics; labeling; unnatural monosaccharides.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylation
  • Alkynes / chemistry
  • Azides / chemistry
  • Biotin / chemistry
  • Biotin / metabolism
  • Cysteine / chemistry*
  • Cysteine / metabolism
  • Glutathione / chemistry
  • Glycosylation
  • HeLa Cells
  • Humans
  • Metabolic Engineering
  • Monosaccharides / chemistry*
  • Monosaccharides / metabolism
  • Peptides / analysis
  • Tandem Mass Spectrometry


  • Alkynes
  • Azides
  • Monosaccharides
  • Peptides
  • Biotin
  • Glutathione
  • Cysteine