Article

β‐Galactoside catabolism within Bifidobacterium

Molecular Microbiology, Wiley, ISSN 0950-382X

Volume 94, 5, 2014

DOI:10.1111/mmi.12815, Dimensions: pub.1006362565, PMID: 25287704,

Affiliations

Organisations

  1. (1) Technical University of Denmark, grid.5170.3, DTU
  2. (2) Ishikawa Prefectural University, grid.410789.3
  3. (3) University of Copenhagen, grid.5254.6, KU
  4. (4) National Food Research Institute, grid.419365.c

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Denmark

Japan

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Europe

Asia

Description

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.

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Technical University of Denmark

University of Copenhagen

Dimensions Citation Indicators

Times Cited: 18

Field Citation Ratio (FCR): 2.24

Relative Citation ratio (RCR): 0.65