Unusual molecular architecture of a human gut microbiota β-mannanase reveals a new CBM family

Unusual molecular architecture of a human gut microbiota β-mannanase reveals a new CBM family | Research Square Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Unusual molecular architecture of a human gut microbiota β-mannanase reveals a new CBM family Natalia Łoś, Ieva Lelėnaitė, William G. T. Willats, Nicolas Terrapon, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8925544/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 14 May, 2026 Read the published version in Cellular and Molecular Life Sciences → Version 1 posted 5 You are reading this latest preprint version Abstract 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, 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-mannan and support their classification as a novel CBM family. To investigate the evolutionary 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. Carbohydrate-binding module β-mannanase Bacteroides glycoside hydrolase family 26 Microbiota Full Text Supplementary Files SupplementaryinformationLosetal.2026.pdf Cite Share Download PDF Status: Published Journal Publication published 14 May, 2026 Read the published version in Cellular and Molecular Life Sciences → Version 1 posted Editorial decision: Minor Revision 27 Mar, 2026 Reviewers agreed at journal 25 Feb, 2026 Reviewers invited by journal 25 Feb, 2026 Editor assigned by journal 21 Feb, 2026 First submitted to journal 20 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information

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