Structural bases for N-glycan processing by mannoside phosphorylase

Acta Crystallogr D Biol Crystallogr. 2015 Jun;71(Pt 6):1335-46. doi: 10.1107/S1399004715006604. Epub 2015 May 14.


The first crystal structure of Uhgb_MP, a β-1,4-mannopyranosyl-chitobiose phosphorylase belonging to the GH130 family which is involved in N-glycan degradation by human gut bacteria, was solved at 1.85 Å resolution in the apo form and in complex with mannose and N-acetylglucosamine. SAXS and crystal structure analysis revealed a hexameric structure, a specific feature of GH130 enzymes among other glycoside phosphorylases. Mapping of the -1 and +1 subsites in the presence of phosphate confirmed the conserved Asp104 as the general acid/base catalytic residue, which is in agreement with a single-step reaction mechanism involving Man O3 assistance for proton transfer. Analysis of this structure, the first to be solved for a member of the GH130_2 subfamily, revealed Met67, Phe203 and the Gly121-Pro125 loop as the main determinants of the specificity of Uhgb_MP and its homologues towards the N-glycan core oligosaccharides and mannan, and the molecular bases of the key role played by GH130 enzymes in the catabolism of dietary fibre and host glycans.

Keywords: GH130 enzymes; N-glycans; glycoside phosphorylases; human gut microbiota.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Models, Molecular
  • Molecular Sequence Data
  • Phosphorylases / chemistry*
  • Polysaccharides / chemistry*
  • Protein Conformation
  • Scattering, Small Angle
  • Sequence Homology, Amino Acid
  • X-Ray Diffraction


  • Polysaccharides
  • Phosphorylases

Associated data

  • PDB/4UDG
  • PDB/4UDI
  • PDB/4UDJ
  • PDB/4UDK