earticle

영어

A recombinant α-l-arabinofuranosidase from Caldicellulosiruptor saccharolyticus was purified by heat treatment and Hi-Trap anion exchange chromatography with a specific activity of 28.2 U mg−1. The native enzyme was a 58-kDa octamer with a molecular mass of 460 kDa, as measured by gel filtration. The catalytic residues and consensus sequences of the
glycoside hydrolase 51 family of α-l-arabinofuranosidases were completely conserved in α-l-arabinofuranosidase from C. saccharolyticus. The maximum enzyme activity was observed at pH 5.5 and 80ºC with a half-life of 49 h at 75ºC. Among aryl-glycoside substrates, the enzyme displayed activity only for p-nitrophenyl-α-l-arabinofuranoside, with a maximum kcat/Km of 220 mM–1 s–1, and p-nitrophenyl-α-l-arabinopyranoside. No activity was observed for arabinan or debranched arabinan. This substrate specificity differs from those of other α-l-arabinofuranosidases. In a 1 mM solution of each sugar, arabino-oligosaccharides with two to five monomer units were completely hydrolyzed to l-arabinose within 13 h in the presence
of 30 U ml−1 of enzyme at 75ºC. The novel substrate specificity and hydrolytic properties for arabino-oligosaccharides demonstrate the potential of α-l-arabinofuranosidase from C. saccharolyticus for use in the commercial production of l-arabinose.