Download MendeleyCrystallographic observation of a covalent catalytic intermediate in a beta-glycosidase.
White, A., Tull, D., Johns, K., Withers, S.G., Rose, D.R.(1996) Nat Struct Biol 3: 149-154
- PubMed: 8564541
- DOI: https://doi.org/10.1038/nsb0296-149
- Primary Citation of Related Structures:
1EXP - PubMed Abstract:
The three-dimensional structure of a catalytically competent glycosyl-enzyme intermediate of a retaining beta-1,4-glycanase has been determined at a resolution of 1.8 A by X-ray diffraction. A fluorinated slow substrate forms an alpha-D-glycopyranosyl linkage to one of the two invariant carboxylates, Glu 233, as supported in solution by 19F-NMR studies. The resulting ester linkage is coplanar with the cyclic oxygen of the proximal saccharide and is inferred to form a strong hydrogen bond with the 2-hydroxyl of that saccharide unit in natural substrates. The active-site architecture of this covalent intermediate gives insights into both the classical double-displacement catalytic mechanism and the basis for the enzyme's specificity.
Organizational Affiliation:
Protein Engineering Network of Centres of Excellence, Ontario Cancer Institute, Toronto, Canada.
