Characterization of a Novel β-L- Arabinofuranosidase in Bifidobacterium longum

Background: -l-Arabinofuranosyl linkages are found in many plant biopolymers, but the degradation enzyme has never been found. Results: A novel -l-arabinofuranosidase was found in Bifidobacterium longum. Conclusion: -l-Arabinofuranosidase plays a key role in Bifidobacterium longum for -l-arabinooligosaccharide usage. Significance: The members of the DUF1680 family might be used for the degradation of plant biopolymers. Pfam DUF1680 (PF07944) is an uncharacterized protein family conserved in many species of bacteria, actinomycetes, fungi, and plants. Previously, we cloned and characterized the hypBA2 gene as a -l-arabinobiosidase in Bifidobacterium longum JCM 1217. In this study, we cloned a DUF1680 family member, the hypBA1 gene, which constitutes a gene cluster with hypBA2. HypBA1 is a novel -l-arabinofuranosidase that liberates l-arabinose from the l-arabinofuranose (Araf)-1,2-Araf disaccharide. HypBA1 also transglycosylates 1-alkanols with retention of the anomeric configuration. Mutagenesis and azide rescue experiments indicated that Glu-338 is a critical residue for catalytic activity. This study provides the first characterization of a DUF1680 family member, which defines a new family of glycoside hydrolases, the glycoside hydrolase family 127.