Motif-Guided Identification of a Glycoside Hydrolase Family 1 α-L-Arabinofuranosidase in Bifidobacterium adolescentis

Members of glycoside hydrolase family 1 (GH1) cleave glycosidic linkages with a variety of physiological roles. Here we report a unique Gill member encoded in the genome of Bifidobacterium adolescentis ATCC 15703. This enzyme, BAD0156, was identified from over 2,000 Gill sequences accumulated in a database by a genome mining approach based on a motif sequence. A recombinant BAD0156 protein was characterized to confirm that this enzyme alone specifically hydrolyzes p-nitrophenyl-alpha-L-arabinofuranoside among the 24 p-nitrophenyl-glycosides examined. Among natural glycosides, alpha-1,5-linked arabino-oligosaccharides served as substrates, but arabinan, debranched arabinan, arabinoxylan, and arabinogalactan did not. A time course analysis of arabino-oligosaccharide hydrolysis indicated that BAD0156 is an exo-acting enzyme. These results suggest that BAD0156 is an alpha-L-arabinofuranosidase. This is the first report of a Gill enzyme that acts specifically on arabinosides, providing information on GH1 substrate specificity.