Gene Cloning, Expression, and Characterization of a Family 51 α-l-Arabinofuranosidase from Streptomyces sp S9

An alpha-l-arabinofuranosidase gene, abf51S9, was cloned from Streptomyces sp. S9 and successfully expressed in Escherichia coli BL21 (DE3). The full-length gene consisted of 1,506 bp and encoded 501 amino acids with a calculated mass of 55.2 kDa. The deduced amino acid sequence was highly homologous with the alpha-l-arabinofuranosidases belonging to family 51 of the glycoside hydrolases. The recombinant protein was purified to electrophoretic homogeneity by Ni-NTA affinity chromatography and subsequently characterized. The optimal pH and temperature for the recombinant enzyme were 6.0 and 60 similar to 65 A degrees C, respectively. The enzyme showed a broad pH range of stability, retaining over 75% of the maximum activity at pH 5.0 to 11.0. The specific activity, K (m), and V (max) with p-nitrophenyl-alpha-l-arabinofuranoside as substrate were 60.0 U mg(-1), 1.45 mM, and 221 mu mol min(-1) mg(-1), respectively. Abf51S9 showed a mild but significant synergistic effect in combination with xylanase on the degradation of oat-spelt xylan and soluble wheat arabinoxylan substrates with a 1.19- and 1.21-fold increase in the amount of reducing sugar released, respectively. These favorable properties make Abf51S9 a good candidate in various industrial applications.