Diamond Publications - Search Results

Search Again...

These results only include publications that have been reviewed and processed by Diamond Light Source. To also view papers that have not yet been processed click here.

You can use the folder icon under Actions to collate papers as required. You can then click on View Folder in the left-hand navigation to review and/or download your folder.

One item found (0 items not approved).

Instruments / Technical Area	Publication Details	Published	Actions
I02-Macromolecular Crystallography I04-1-Macromolecular Crystallography (fixed wavelength) I04-Macromolecular Crystallography	An epoxide intermediate in glycosidase catalysis Lukasz F. Sobala , Gaetano Speciale , Sha Zhu , Lluı́s Raich , Natalia Sannikova , Andrew J. Thompson , Zalihe Hakki , Dan Lu , Saeideh Shamsi Kazem Abadi , Andrew R. Lewis , Vı́ctor Rojas-cervellera , Ganeko Bernardo-seisdedos , Yongmin Zhang , Oscar Millet , Jesús Jiménez-barbero , Andrew J. Bennet , Matthieu Sollogoub , Carme Rovira , Gideon J. Davies , Spencer J. Williams Acs Central Science DOI: 10.1021/acscentsci.0c00111 Diamond Proposal Number(s): [9948, 13587] Open Access Show Abstract ▼ Abstract: Retaining glycoside hydrolases cleave their substrates through stereochemical retention at the anomeric position. Typically, this involves two-step mechanisms using either an enzymatic nucleophile via a covalent glycosyl enzyme intermediate or neighboring-group participation by a substrate-borne 2-acetamido neighboring group via an oxazoline intermediate; no enzymatic mechanism with participation of the sugar 2-hydroxyl has been reported. Here, we detail structural, computational, and kinetic evidence for neighboring-group participation by a mannose 2-hydroxyl in glycoside hydrolase family 99 endo-α-1,2-mannanases. We present a series of crystallographic snapshots of key species along the reaction coordinate: a Michaelis complex with a tetrasaccharide substrate; complexes with intermediate mimics, a sugar-shaped cyclitol β-1,2-aziridine and β-1,2-epoxide; and a product complex. The 1,2-epoxide intermediate mimic displayed hydrolytic and transfer reactivity analogous to that expected for the 1,2-anhydro sugar intermediate supporting its catalytic equivalence. Quantum mechanics/molecular mechanics modeling of the reaction coordinate predicted a reaction pathway through a 1,2-anhydro sugar via a transition state in an unusual flattened, envelope (E3) conformation. Kinetic isotope effects (kcat/KM) for anomeric-2H and anomeric-13C support an oxocarbenium ion-like transition state, and that for C2-18O (1.052 ± 0.006) directly implicates nucleophilic participation by the C2-hydroxyl. Collectively, these data substantiate this unprecedented and long-imagined enzymatic mechanism.	Apr 2020

Instruments / Technical Area

Publication Details

Published

Actions

I02-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I04-Macromolecular Crystallography

An epoxide intermediate in glycosidase catalysis