A Beta1-6/Beta1-3 Galactosidase from Bifidobacterium Animalis Subsp. Lactis Bl-04 Gives Insight Into Sub-Specificities of Beta-Galactoside Catabolism within Bifidobacterium.Viborg, A.H., Fredslund, F., Katayama, T., Nielsen, S.K., Svensson, B., Kitaoka, M., Leggio, L.L., Abou Hachem, M.
(2014) Mol.Microbiol. --: --
- PubMed: 25287704
- DOI: 10.1111/mmi.12815
- Primary Citation of Related Structures:
- PubMed Abstract:
The Bifidobacterium genus harbours several health promoting members of the gut microbiota. Bifidobacteria display metabolic specialization by preferentially utilizing dietary or host-derived β-galactosides. This study investigates the biochemistry an ...
The Bifidobacterium genus harbours several health promoting members of the gut microbiota. Bifidobacteria display metabolic specialization by preferentially utilizing dietary or host-derived β-galactosides. This study investigates the biochemistry and structure of a glycoside hydrolase family 42 (GH42) β-galactosidase from the probiotic Bifidobacterium animalis subsp. lactis Bl-04 (BlGal42A). BlGal42A displays a preference for undecorated β1-6 and β1-3 linked galactosides and populates a phylogenetic cluster with close bifidobacterial homologues implicated in the utilization of N-acetyl substituted β1-3 galactosides from human milk and mucin. A long loop containing an invariant tryptophan in GH42, proposed to bind substrate at subsite + 1, is identified here as specificity signature within this clade of bifidobacterial enzymes. Galactose binding at the subsite - 1 of the active site induced conformational changes resulting in an extra polar interaction and the ordering of a flexible loop that narrows the active site. The amino acid sequence of this loop provides an additional specificity signature within this GH42 clade. The phylogenetic relatedness of enzymes targeting β1-6 and β1-3 galactosides likely reflects structural differences between these substrates and β1-4 galactosides, containing an axial galactosidic bond. These data advance our molecular understanding of the evolution of sub-specificities that support metabolic specialization in the gut niche.
Enzyme and Protein Chemistry, Department of Systems Biology, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark.