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 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.
Related Citations:
Crystal Structure of the Catalytic Domain of the Beta-1,4-Glycanase Cex from Cellulomonas Fimi White, A., Withers, S.G., Gilkes, N.R., Rose, D.R. (1994) Biochemistry 33: 12546
Crystallization and Preliminary X-Ray Diffraction Analysis of the Catalytic Domain of Cex, an Exo-Beta-1,4-Glucanase and Beta-1,4-Xylanase from the Bacterium Cellulomonas Fimi Bedarkar, S., Gilkes, N.R., Kilburn, D.G., Kwan, E., Rose, D.R., Miller Junior, R.C., Warren, R.A., Withers, S.G. (1992) J Mol Biol 228: 693
Organizational Affiliation:
Protein Engineering Network of Centres of Excellence, Ontario Cancer Institute, Toronto, Canada.
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