Catalysis by Hen Egg-White Lysozyme Proceeds Via a Covalent IntermediateVocadlo, D.J., Davies, G.J., Laine, R., Withers, S.G.
(2001) Nature 412: 835
- PubMed: 11518970
- DOI: 10.1038/35090602
- PubMed Abstract:
- Site Directed Mutagenesis of the Catalytic Residues Asp-52 and Glu-35 of Chicken Egg White Lysozyme
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(1989) Proc.Natl.Acad.Sci.USA 86: 133
- Lysozyme Revisited: Crystallographic Evidence for Distortion of an N-Acetylmuramic Residue Bound in Subsite D
Strydnaka, N.C.J.,James, M.N.G.
(1991) J.Mol.Biol. 220: 401
- Structure of Hen Egg-White Lysozyme: A Three Dimensional Fourier Analysis at 2.0A Resolution
Blake, C.C.F.,Koenig, D.F.,Mair, G.A.,North, A.C.T.,Phillips, D.C.,Sarma, V.R.
(1965) Nature 206: 757
Hen egg-white lysozyme (HEWL) was the first enzyme to have its three-dimensional structure determined by X-ray diffraction techniques. A catalytic mechanism, featuring a long-lived oxocarbenium-ion intermediate, was proposed on the basis of model-bui ...
Hen egg-white lysozyme (HEWL) was the first enzyme to have its three-dimensional structure determined by X-ray diffraction techniques. A catalytic mechanism, featuring a long-lived oxocarbenium-ion intermediate, was proposed on the basis of model-building studies. The 'Phillips' mechanism is widely held as the paradigm for the catalytic mechanism of beta-glycosidases that cleave glycosidic linkages with net retention of configuration of the anomeric centre. Studies with other retaining beta-glycosidases, however, provide strong evidence pointing to a common mechanism for these enzymes that involves a covalent glycosyl-enzyme intermediate, as previously postulated. Here we show, in three different cases using electrospray ionization mass spectrometry, a catalytically competent covalent glycosyl-enzyme intermediate during the catalytic cycle of HEWL. We also show the three-dimensional structure of this intermediate as determined by X-ray diffraction. We formulate a general catalytic mechanism for all retaining beta-glycosidases that includes substrate distortion, formation of a covalent intermediate, and the electrophilic migration of C1 along the reaction coordinate.
Protein Engineering Network of Centres of Excellence and the Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.