Enzymology
A Bacteroidetes locus dedicated to fungal 1,6-β-glucan degradation: Unique substrate conformation drives specificity of the key endo-1,6-β-glucanase
Glycans are major nutrients available to the human gut microbiota. The Bacteroides are generalist glycan degraders, and this function is mediated largely by polysaccharide utilization loci (PULs). The genomes of several Bacteroides species contain a PUL, PUL1,6-β-glucan, that was predicted to target mixed linked plant 1,3;1,4-β-glucans. To test this hypothesis we characterized the proteins encoded by this locus in Bacteroides thetaiotaomicron, a member of the human gut microbiota. We show here that PUL1,6-β-glucan does not orchestrate the degradation of a plant polysaccharide but targets a fungal cell wall glycan, 1,6-β-glucan, which is a growth substrate for the bacterium.The GH130 Family of Mannoside Phosphorylases Contains Glycoside Hydrolases That Target β-1,2-Mannosidic Linkages in Candida Mannan
Background: A cohort of a family of mannose phosphorylases lack phosphate binding residues, suggesting that they display non-phosphorylase activities.Results: The non-phosphorylase enzymes were shown to be β-mannosidases.Conclusion: Replacing basic phosphate binding residues with carboxylic amino acids converts mannoside phosphorylases into glycoside hydrolases.Significance: Functional phylogeny can be used to distinguish between closely related glycan phosphorylases and glycoside hydrolases.
