Methods of Glycan Sequencing

In order to confirm the structures, the sequence of a particular glycan molecule can be elucidated by sequential exoglycosidase digestion. Most exoglycosidases are specific for the sugar and the anomericity (α or β) of the linkage that they will recognize and cut. The researcher can use specific exoglycosidases to determine the anomericity and type of terminal sugar residues present on the glycan being analyzed. Some exoglycosidases will cleave linkages of a given residue only when they are present at a specific position on the monosaccharide, providing detailed structural conclusions (1, 2)

An alternative method of non-enzymatic analysis, such as mass spectrometry collision induced dissociation, is often used with permethylated glycans to determine the structure of the glycan. The spectral information along with knowledge of biosynthetic pathways allows for determination of the underlying glycan structure(s) with great accuracy (3,4). However, and similar to protein MS analysis, the access to well curated databases is essential in order to draw valid conclusions.

Finally, trypsin or other proteases are often used on glycoproteins to elucidate by mass spectrometry the glycan diversity at any given region within the polypeptide chain (5).

1. Mariño K, et al. (2010) Nat Chem Biol. 6(10):713-23. PMID: 20852609
2. Lazar IM, et al. (2011) Electrophoresis. 32(1):3-13. PMID: 21171109
3. Zaia J. (2010) OMICS. 14(4):401-18. PMID: 20443730
4. North SJ. et al. (2009) Curr Opin Struct Biol. 19(5):498-506. PMID: 19577919
5. Geyer, H., Geyer, R. (2006) Biochim Biophys Acta. 1764(12):1853-69. PMID: 17134948