Download MendeleyCatalysis by Hen Egg-White Lysozyme Proceeds Via a Covalent Intermediate
Vocadlo, D.J., Davies, G.J., Laine, R., Withers, S.G.(2001) Nature 412: 835
- PubMed: 11518970
- DOI: https://doi.org/10.1038/35090602
- Primary Citation of Related Structures:
1H6M - PubMed Abstract:
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.
Organizational Affiliation:
Protein Engineering Network of Centres of Excellence and the Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
