Catalysis by hen egg-white lysozyme proceeds via a covalent intermediate

D J Vocadlo, G J Davies, R Laine, S G Withers

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)835-838
Number of pages4
JournalNature
Volume412
Issue number6849
DOIs
Publication statusPublished - 23 Aug 2001

Bibliographical note

© 2001 Nature Publishing Group

Keywords

  • ACTIVE-SITE
  • BETA-GLUCOSIDASE
  • LEAVING GROUP
  • HYDROLYSIS
  • DISTORTION
  • MECHANISM
  • INSIGHTS
  • MUTANTS
  • ACID

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