Two Novel α- l -Arabinofuranosidases from Bifidobacterium longum subsp. longum Belonging to Glycoside Hydrolase Family 43 Cooperatively Degrade Arabinan

We identified two novel α-l -arabinofuranosidases, BlArafC and BlArafB, fromB. longum subsp.longum JCM 1217, both of which are predicted to be extracellular membrane-bound enzymes. The former specifically acts on α1,2/3-l -arabinofuranosyl linkages, while the latter acts on the α1,5-l -arabinofuranosyl linkage. These enzymes cooperatively degrade arabinan and are required for the efficient growth of bifidobacteria in arabinan-containing medium. The genes encoding these enzymes are located side by side in a gene cluster involved in metabolic pathways for plant-derived polysaccharides, which may confer adaptability in adult intestines.