1h6m

From Proteopedia

Revision as of 14:25, 5 November 2007

COVALENT GLYCOSYL-ENZYME INTERMEDIATE OF HEN EGG WHITE LYSOZYME

Overview

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.

About this Structure

1H6M is a Single protein structure of sequence from Gallus gallus with NA as ligand. Active as Lysozyme, with EC number 3.2.1.17 Structure known Active Sites: NA, NAG and NUC. Full crystallographic information is available from OCA.

Reference

Catalysis by hen egg-white lysozyme proceeds via a covalent intermediate., Vocadlo DJ, Davies GJ, Laine R, Withers SG, Nature. 2001 Aug 23;412(6849):835-8. PMID:11518970

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