Vocadlo, D J, Davies, G J, Laine, R and Withers, S G (2001) Catalysis by hen egg-white lysozyme proceeds via a covalent intermediate. Nature. pp. 835-838. ISSN 0028-0836Full text available as:
Hen egg-white lysozyme (HEWL) was the first enzyme to have its three-dimensional structure determined by X-ray diffraction techniques(1). A catalytic mechanism, featuring a long-lived oxo-carbenium-ion intermediate, was proposed on the basis of model-building studies(2). 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(3). 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 Xray 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.
|Copyright, Publisher and Additional Information:||© 2001 Nature Publishing Group|
|Keywords:||ACTIVE-SITE, BETA-GLUCOSIDASE, LEAVING GROUP, HYDROLYSIS, DISTORTION, MECHANISM, INSIGHTS, MUTANTS, ACID|
|Academic Units:||The University of York > Chemistry (York)|
|Depositing User:||Repository Officer|
|Date Deposited:||13 Oct 2004|
|Last Modified:||17 Oct 2013 14:34|