| Structural highlights
Function
LNBB_BIFB1 Present in the infant gut, this enzyme is involved in the assimilation of type-1 human milk oligosaccharides (HMOs). It hydrolyzes via a retaining mechanism the beta-D-GlcNAc-(1->3)-beta-D-Gal linkage in lacto-N-tetraose (LNT or beta-D-Gal-(1->3)-beta-D-GlcNAc-(1->3)-beta-D-Gal-(1->4)-D-Glc), an abundant HMO unique to human breast milk, releasing lacto-N-biose (LNB or beta-D-Gal-(1->3)-D-GlcNAc) and lactose (PubMed:18469123, PubMed:23479733). Is a key enzymatic factor for growth and proliferation of B.bifidum in the gut ecosystem of breast-fed infants (Probable). Has substrate preference for unmodified beta-linked LNB since it does not hydrolyze the fucosylated forms of lacto-N-tetraose (lacto-N-fucopentaose I and II) or lacto-N-neotetraose. Is also able to display transglycosylation activity in vitro (PubMed:18469123).[1] [2] [3]
Publication Abstract from PubMed
Bifidobacterium bifidum, a predominant colonizer of the infant gut, utilizes lacto-N-biose I (LNB), a prominent component of human milk oligosaccharides (HMOs), through a dedicated metabolic pathway. Among a diverse set of extracellular glycosidases involved in HMO degradation, lacto-N-biosidase (LnbB) plays a pivotal role by releasing LNB. We investigated the structure and function of the carbohydrate-binding module family 32 (CBM32) domain located at the C-terminus of the glycoside hydrolase family 20 catalytic domain in LnbB. Isothermal titration calorimetry showed that CBM32 binds LNB with a dissociation constant (K(d)) of 98 mum. The crystal structure of the CBM32 complexed with LNB reveals the molecular basis for its specific recognition. Impact statement Bifidobacteria are beneficial gut microbes, and infant-associated strains establish symbiosis by degrading human milk oligosaccharides. This study uncovers the molecular mechanism by which Bifidobacterium bifidum captures lacto-N-biose I, a key disaccharide, functioning as a cross-feeder that promotes the growth of other bifidobacteria and supports the infant gut ecosystem.
Structural insights into lacto-N-biose I recognition by a family 32 carbohydrate-binding module from Bifidobacterium bifidum.,Zhang X, Sunagawa N, Kashima T, Igarashi K, Miyanaga A, Fushinobu S FEBS Lett. 2025 Nov 7. doi: 10.1002/1873-3468.70217. PMID:41204437[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Wada J, Ando T, Kiyohara M, Ashida H, Kitaoka M, Yamaguchi M, Kumagai H, Katayama T, Yamamoto K. Bifidobacterium bifidum lacto-N-biosidase, a critical enzyme for the degradation of human milk oligosaccharides with a type 1 structure. Appl Environ Microbiol. 2008 Jul;74(13):3996-4004. doi: 10.1128/AEM.00149-08., Epub 2008 May 9. PMID:18469123 doi:http://dx.doi.org/10.1128/AEM.00149-08
- ↑ Ito T, Katayama T, Hattie M, Sakurama H, Wada J, Suzuki R, Ashida H, Wakagi T, Yamamoto K, Stubbs KA, Fushinobu S. Crystal structures of a glycoside hydrolase family 20 lacto-N-biosidase from Bifidobacterium bifidum. J Biol Chem. 2013 Apr 26;288(17):11795-806. doi: 10.1074/jbc.M112.420109. Epub, 2013 Mar 11. PMID:23479733 doi:10.1074/jbc.M112.420109
- ↑ Ito T, Katayama T, Hattie M, Sakurama H, Wada J, Suzuki R, Ashida H, Wakagi T, Yamamoto K, Stubbs KA, Fushinobu S. Crystal structures of a glycoside hydrolase family 20 lacto-N-biosidase from Bifidobacterium bifidum. J Biol Chem. 2013 Apr 26;288(17):11795-806. doi: 10.1074/jbc.M112.420109. Epub, 2013 Mar 11. PMID:23479733 doi:10.1074/jbc.M112.420109
- ↑ Zhang X, Sunagawa N, Kashima T, Igarashi K, Miyanaga A, Fushinobu S. Structural insights into lacto-N-biose I recognition by a family 32 carbohydrate-binding module from Bifidobacterium bifidum. FEBS Lett. 2025 Nov 7. PMID:41204437 doi:10.1002/1873-3468.70217
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