A β-mannanase with a lysozyme-like fold and a novel molecular catalytic mechanism

Jin, Yi ORCID: https://orcid.org/0000-0002-6927-4371, Petricevic, Marija, John, Alan, Raich, Lluís, Jenkins, Huw, Portela De Souza, Leticia, Cuskin, Fiona, Gilbert, Harry J., Rovira, Carme, Goddard-Borger, Ethan D., Williams, Spencer J. and Davies, Gideon J. 2016. A β-mannanase with a lysozyme-like fold and a novel molecular catalytic mechanism. ACS Central Science 2 (12) , pp. 896-903. 10.1021/acscentsci.6b00232

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Abstract

The enzymatic cleavage of β-1,4-mannans is achieved by endo-β-1,4-mannanases, enzymes involved in germination of seeds and microbial hemicellulose degradation, and which have increasing industrial and consumer product applications. β-Mannanases occur in a range of families of the CAZy sequence-based glycoside hydrolase (GH) classification scheme including families 5, 26, and 113. In this work we reveal that β-mannanases of the newly described GH family 134 differ from other mannanase families in both their mechanism and tertiary structure. A representative GH family 134 endo-β-1,4-mannanase from a Streptomyces sp. displays a fold closely related to that of hen egg white lysozyme but acts with inversion of stereochemistry. A Michaelis complex with mannopentaose, and a product complex with mannotriose, reveal ligands with pyranose rings distorted in an unusual inverted chair conformation. Ab initio quantum mechanics/molecular mechanics metadynamics quantified the energetically accessible ring conformations and provided evidence in support of a 1C4 → 3H4‡ → 3S1 conformational itinerary along the reaction coordinate. This work, in concert with that on GH family 124 cellulases, reveals how the lysozyme fold can be co-opted to catalyze the hydrolysis of different polysaccharides in a mechanistically distinct manner.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Subjects:	Q Science > QD Chemistry
Publisher:	American Chemical Society
ISSN:	2374-7951
Date of First Compliant Deposit:	22 June 2017
Last Modified:	06 Jan 2024 02:23
URI:	https://orca.cardiff.ac.uk/id/eprint/100306

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