Structural Identification of O-linked oligosaccharides using exoglycosidases and MSn together with UniCarb-DB fragment spectra comparison

Liaqat Ali, Diarmuid T. Kenny, Catherine A. Hayes, Niclas G. Karlsson

Research output: Contribution to journalArticlepeer-review


The availability of specific exoglycosidases alongside a spectral library of Olinked oligosaccharide collision induced dissociation (CID) MS fragments, UniCarb-DB, provides a pathway to make the elucidation of O-linked oligosaccharides more efficient. Here, we advise an approach of exoglycosidase-digestion of O-linked oligosaccharide mixtures, for structures that do not provide confirmative spectra. The combination of specific exoglycosidase digestion and MS2 matching of the exoglycosidase products with structures from UniCarb-DB, allowed the assignment of unknown structures. This approach was illustrated by treating sialylated core 2 O-linked oligosaccharides, released from the human synovial glycoprotein (lubricin), with a α2-3 specific sialidase. This methodology demonstrated the exclusive 3 linked nature of the sialylation of core 2 oligosaccharides on lubricin. When specific exoglycosidases were not available, MS3 spectral matching using standards was used. This allowed the unusual 4-linked terminal GlcNAc epitope in a porcine stomach to be identified in the GlcNAc1-4Galβ1- 3(GlcNAcβ1-6)GalNAcol structure, indicating the antibacterial epitope GlcNAcα1-4. In total, 13 structures were identified using exoglycosidase and MSn, alongside UniCarb-DB fragment spectra comparison. UniCarb-DB could also be used to identify the specificity of unknown exoglycosidases in human saliva. Endogenous salivary exoglycosidase activity on mucin oligosaccharides could be monitored by comparing the generated tandem MS spectra with those present in UniCarb-DB, showing that oral exoglycosidases were dominated by sialidases with a higher activity towards 3-linked sialic acid rather than 6-linked sialic acid.

Original languageEnglish (US)
Pages (from-to)648-666
Number of pages19
Issue number4
StatePublished - Oct 8 2012


  • Exoglycosidases
  • Glycomics
  • Mass spectrometry
  • Mucin

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Molecular Biology


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