Hydrolysis of Arabinoxylo-oligosaccharides by α-L-Arabinofuranosidases and β-D-Xylosidase from .

Two α-L-arabinofuranosidases (BfdABF1 and BfdABF3) and a β-D-xylosidase (BfdXYL2) genes were cloned from ATCC 27679, and functionally expressed in BL21(DE3). BfdABF1 showed the highest activity in 50 mM sodium acetate buffer at pH 5.0 and 25°C. This -enzyme could hydrolyze -nitrophenyl arabinofuranoside, arabino-oligosaccharides (AOS), arabinoxylo-oligosaccharides (AXOS) such as 3-α-L-arabinofuranosyl-xylobiose (AX), and 2-α-Larabinofuranosyl-xylotriose (AXX), whereas hardly hydrolyzed polymeric substrates such as debranched arabinan and arabinoxylans. BfdABF1 is a typical -ABF with the higher specific activity on the oligomeric substrates than the polymers. It prefers to α-(1,2)-L-arabinofuranosidic linkages compared to α-(1,3)-linkages. Especially, BfdABF1 could slowly hydrolyze 2,3-di-α-L-arabinofuranosyl-xylotriose (AXX). Meanwhile, BfdABF3 showed the highest activity in sodium acetate at pH 6.0 and 50°C, and it has the exclusively high activities on AXOS such as AX and AXX. BfdABF3 mainly catalyzes the removal of L-arabinose side chains from various AXOS. BfdXYL2 exhibited the highest activity in sodium citrate at pH 5.0 and 55°C, and it specifically hydrolyzed -nitrophenyl xylopyranoside and xylo-oligosaccharides (XOS). Also, BfdXYL2 could slowly hydrolyze AOS and AXOS such as AX. Based on the detailed hydrolytic modes of action of three -hydrolases (BfdABF1, BfdABF3, and BfdXYL2) from , their probable roles in the hemiceulloseutilization system of Bf. dentium are proposed in the present study. These intracellular -hydrolases can synergistically produce L-arabinose and D-xylose from various AOS, XOS, and AXOS.