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Lookup NU author(s): Natalia Los, Dr Ieva LelenaiteORCiD, Professor William WillatsORCiD, Dr Hamish Yau, Dr Elisabeth LoweORCiD, Dr David BolamORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© The Author(s) 2026. β-mannans are plant structural and storage polysaccharides prevalent in the human diet. Their degradation in the gastrointestinal tract is mediated by the human gut microbiota (HGM) through expression of a plethora of carbohydrate-active enzymes (CAZymes), although our understanding of the details of mannan breakdown is lacking. In this study, a prominent HGM member, Bacteroides cellulosilyticus (Bc), was found to be exceptionally efficient at utilising β-mannans, mediated by the expression of a single polysaccharide utilisation locus (PUL). Amongst the predicted surface CAZymes encoded in the PUL, we identified a family 26 glycoside hydrolase of an unusual molecular architecture. BcWH2_GH26 contains a putative carbohydrate-binding module (CBM) directly intercalated into its catalytic domain, unlike classical CBMs which are located at the N- or C-termini of the catalytic domain. Phylogenetic and functional analyses of this internal CBM, and a homologue from another mannan user Bacteroides uniformis, revealed a narrow specificity for β-mannans and support their classification as a novel CBM family, CBM112. To investigate the functional basis for the unusual enzyme architecture, the effect of the CBM on the catalytic activity of the enzyme was assessed. No significant differences in the kinetic parameters were found between the full-length and CBM deletion constructs against both soluble and insoluble mannans. The potential role of the internal CBM in enzyme function is discussed in the context of the likely localisation of the BcWH2_GH26 in the outer membrane utilisome encoded by the Bc mannan PUL.
Author(s): Los N, Lelenaite I, Willats WGT, Terrapon N, Morales-Garcia AL, Yau HCL, Lowe EC, Bolam DN
Publication type: Article
Publication status: Published
Journal: Cellular and Molecular Life Sciences
Year: 2026
Volume: 83
Print publication date: 13/07/2026
Online publication date: 14/05/2026
Acceptance date: 28/04/2026
Date deposited: 20/07/2026
ISSN (print): 1420-682X
ISSN (electronic): 1420-9071
Publisher: Springer Nature
URL: https://doi.org/10.1007/s00018-026-06241-x
DOI: 10.1007/s00018-026-06241-x
Data Access Statement: The data supporting the findings of this study are available within the article and in its Supplementary Information.
PubMed id: 42133002
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