The 2,367-bp ORF of TtAFase from Thermotoga thermarum DSM 5069 encodes a calculated 90-kDa alpha-l-arabinofuranosidase (TtAFase), which does not belonging to any reported glycosyl hydrolase families alpha-l-arabinofuranosidases in the database and represents a novel one of glycosyl hydrolase family 2. The purified recombinant TtAFase produced in Escherichia coli BL21 (DE3) had optimum activity at pH 5.5 and at 80 A degrees C. It was stable up to 80 A degrees C and from pH 4.5-8.5. Kinetic experiments at 80 A degrees C with p-nitrophenyl alpha-l-arabinofuranoside as a substrate gave a K (m) of 0.77 mM, V (max) of 2.3 mu mol mg(-1) min(-1) and k (cat) of 4.5 s(-1). The enzyme had no apparent requirement of metal ions for activity, and its activity was significantly inhibited by Cu2+ or Zn2+.