Screening, identification, and characterization of α-xylosidase from a soil metagenome.

A novel α-xylosidase, MeXyl31, was isolated and characterized from a soil metagenomic library. The amino acid sequence of MeXyl31 showed a slight homology with other characterized α-xylosidases. The optimal pH and temperature of recombinant MeXyl31 were pH 5.5 and 45°C, respectively. Recombinant MeXyl31 had a higher α-xylosidase activity toward pNP α-d-xylopyranoside than pNP α-d-glucopyranoside, isoprimeverose, and other xyloglucan oligosaccharides. The kcat/Km value toward pNP α-d-xylopyranoside was about 750-fold higher than that of isoprimeverose. MeXyl31 activity was strongly inactivated in the presence of zinc and copper ions. MeXyl31 is the first α-xylosidase isolated from the metagenome and, relative to other xyloglucan oligosaccharides, shows higher activity toward pNP α-d-xylopyranoside.