Fucosidases from the human gut symbiont Ruminococcus gnavus

The availability and repartition of fucosylated glycans within the gastrointestinal tract contributes to the adaptation of gut bacteria species to ecological niches. To access this source of nutrients, gut bacteria encode alpha-l-fucosidases (fucosidases) which catalyze the hydrolysis of terminal alpha-l-fucosidic linkages. We determined the substrate and linkage specificities of fucosidases from the human gut symbiont Ruminococcus gnavus. Sequence similarity network identified strain-specific fucosidases in R. gnavus ATCC 29149 and E1 strains that were further validated enzymatically against a range of defined oligosaccharides and glycoconjugates. Using a combination of glycan microarrays, mass spectrometry, isothermal titration calorimetry, crystallographic and saturation transfer difference NMR approaches, we identified a fucosidase with the capacity to recognize sialic acid-terminated fucosylated glycans (sialyl Lewis X/A epitopes) and hydrolyze alpha 1-3/4 fucosyl linkages in these substrates without the need to remove sialic acid. Molecular dynamics simulation and docking showed that 3 '-Sialyl Lewis X (sLeX) could be accommodated within the binding site of the enzyme. This specificity may contribute to the adaptation of R. gnavus strains to the infant and adult gut and has potential applications in diagnostic glycomic assays for diabetes and certain cancers.

Automated summary

The study focuses on how gut bacteria adapt to ecological niches by utilizing fucosylated glycans, identifying a fucosidase enzyme with specific substrate and linkage preferences. This enzyme has the ability to recognize and hydrolyze specific fucosyl linkages, potentially contributing to the adaptation of R. gnavus strains in the infant and adult gut microbiome.