Crystal structure and snapshots along the reaction pathway of a family 51 α-L-arabinofuranosidase

Klaus Hövel, Dalia Shallom, Karsten Niefind, Valery Belakhov, Gil Shoham, Timor Baasov, Yuval Shoham*, Dietmar Schomburg

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

128 Scopus citations


High-resolution crystal structures of α-L-arabinofuranosidase from Geobacillus stearothermophilus T-6, a family 51 glycosidase, are described. The enzyme is a hexamer, and each monomer is organized into two domains: a (β/α)8-barrel and a 12-stranded β sandwich with jelly-roll topology. The structures of the Michaelis complexes with natural and synthetic substrates, and of the transient covalent arabinofuranosyl-enzyme intermediate represent two stable states in the double displacement mechanism, and allow thorough examination of the catalytic mechanism. The arabinofuranose sugar is tightly bound and distorted by an extensive network of hydrogen bonds. The two catalytic residues are 4.7 Å apart, and together with other conserved residues contribute to the stabilization of the oxocarbenium ion-like transition state via charge delocalization and specific protein-substrate interactions. The enzyme is an anti-protonator, and a 1.7 Å electrophilic migration of the anomeric carbon takes place during the hydrolysis.

Original languageAmerican English
Pages (from-to)4922-4932
Number of pages11
JournalEMBO Journal
Issue number19
StatePublished - 1 Oct 2003


  • Arabinofuranosidase
  • Clan GH-A glycosidase
  • Enzyme mechanism
  • Glycoside hydrolase family 51/X-ray crystallography


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