The catalytic mechanism of 'retaining' beta-glycosidases has been the subject of considerable interest and debate for many years. The visualization of a covalent glycosyl enzyme intermediate by X-ray crystallography was first accomplished with a saccharide substrate substituted with fluorine at its 2-position ...
The catalytic mechanism of 'retaining' beta-glycosidases has been the subject of considerable interest and debate for many years. The visualization of a covalent glycosyl enzyme intermediate by X-ray crystallography was first accomplished with a saccharide substrate substituted with fluorine at its 2-position. The structure implicated major roles for residue His 205 and for the 2-hydroxyl position of the proximal saccharide in binding and catalysis. Here we have studied the kinetic behavior of various His 205 mutants. One of these mutants, a double mutant H205N/E127A, has been used to stabilize a covalent glycosyl-enzyme intermediate involving an unsubstituted sugar, permitting crystallographic analysis of the interactions between its 2-hydroxyl group and the enzyme.
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 and Department of Medical Biophysics, University of Toronto, Canada.
Download Mendeley
