The biochemical properties of a putative beta-1,3-xylanase from the hyperthermophilic eubacterium Thermotoga neapolitana DSM 4359 were determined from a recombinant protein (TnXyn26A) expressed in Escherichia coli. This enzyme showed specific hydrolytic activity against beta-1,3-xylan and released beta-1,3-xylobiose and beta-1,3-xylotriose as main products. It displayed maximum activity at 85 A degrees C during a 10-min incubation, and its activity half-life was 23.9 h at 85 A degrees C. Enzyme activity was stable in the pH range 3-10, with pH 6.5 being optimal. Enzyme activity was significantly inhibited by the presence of N-bromosuccinimide (NBS). The insoluble beta-1,3-xylan K (m) value was 10.35 mg/ml and the k (cat) value was 588.24 s(-1). The observed high thermostability and catalytic efficiency of TnXyn26A is both industrially desirable and also aids an understanding of the chemistry of its hydrolytic reaction.