## 2 Experimental Section
### Enzyme Assays  
The xylanase activity was determined by mixing 25 \(\mu\)L of enzyme solution with 50 \(\mu\)L of oat spelt xylan (10 mg\(\cdot\)mL\({}^{-1}\)) in 50 mmol\(\cdot\)L\({}^{-1}\) sodium acetate buffer, pH 5.0, at 50 \({}^{\circ}\)C for 30 min, as described by [PERSON] _et al._[14]. The release of the reducing sugar was measured using the 3,5-dinitrosalicylic acid (DNS) method [15], and the xylanase activity was expressed as micromoles of reducing sugar released per min per milliliter (IU\(\cdot\)mL\({}^{-1}\)). The \(\beta\)-1,3-glucanase, \(\beta\)-1,4-glucanase and \(\beta\)-mannanase assays were performed under the same conditions as described above. The activity against filter paper was measured as described by [PERSON] [16]. \(\beta\)-Xylosidase, \(\alpha\)-arabinofuranosidase, \(\beta\)-glucosidase and \(\beta\)-mannosidase activities were determined as reported elsewhere [17]. For the kinetics experiments, the soluble and insoluble fractions of oat spelt and birchwood xylans were used as substrates in a concentration range of 6.0-26.7 mg\(\cdot\)mL\({}^{-1}\). The substrates were prepared as described by [PERSON] _et al._[14]. K\({}_{\mathrm{m}}\) and V\({}_{\mathrm{max}}\) were estimated from the Michaelis-Menten equation with a non-linear regression data analysis program (Enzfitter) [18]. The effect of temperature on Xyl-O1 activity was determined in the temperature range of 30 to 80 \({}^{\circ}\)C in 35 mmol\(\cdot\)L\({}^{-1}\) sodium acetate buffer, pH 5.0. To determine the effect of pH on Xyl-O1 activity at 50 \({}^{\circ}\)C, the Xyl-O1 activity in the pH range of 3.0 to 9.0 was determined. The following buffers were used for these experiments: 50 mmol\(\cdot\)L\({}^{-1}\) sodium acetate (pH 3.0-6.0), 50 mmol\(\cdot\)L\({}^{-1}\) sodium phosphate (pH 6.5-7.5), and 50 mmol\(\cdot\)L\({}^{-1}\) Tris-HCl (pH 7.0-9.0). All buffers, regardless of pH, were adjusted to the same ionic strength with NaCl [19]. Xyl-O1 stability was determined by pre-incubating the enzyme at pH 7.0 at either 50 or 55 \({}^{\circ}\)C. At various time points, aliquots were withdrawn, and the residual activity was measured in the presence of 25 mmol\(\cdot\)L\({}^{-1}\) sodium acetate, pH 6.0 (ionic strength adjusted with NaCl), at 50 \({}^{\circ}\)C. Purified xylanase activity was determined in the presence of the metal ions Ag\({}^{+}\), K\({}^{+}\), Na\({}^{+}\), Co\({}^{2+}\), Ca\({}^{2+}\), Cu\({}^{2+}\), Fe\({}^{2+}\), Hg\({}^{2+}\), Mg\({}^{2+}\), Mn\({}^{2+}\), Zn\({}^{2+}\), Al\({}^{3+}\) and Fe\({}^{3+}\) at final concentrations of 1.0 and 10 mmol\(\cdot\)L\({}^{-1}\). The effects of the reagents 1.0 mmol\(\cdot\)L\({}^{-1}\) N-bromosuccinimide (NBS), 2.0 mmol\(\cdot\)L\({}^{-1}\) 5,5-dithio-bis-(2-nitrobenzoic acid) (DTNB) and 2,2-dithiodipyridine, 5.0 mmol\(\cdot\)L\({}^{-1}\) l-tryptophan, iodoacetamide, diethyl pyrocarbonate (DEPC), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and \(\beta\)-mercaptoethanolethanol, and 20 mmol\(\cdot\)L\({}^{-1}\) DTT (1,4-dithiothreitol), l-cysteine and sodium dodecyl sulfate (SDS) were also determined in the presence of 25 mmol\(\cdot\)L\({}^{-1}\) sodium acetate, pH 6.0 (ionic strength adjusted with NaCl), at 50 \({}^{\circ}\)C. Prior to these tests, the purified enzyme was added to either the ions or the reagents and pre-incubated for 20 min at 28 \({}^{\circ}\)C. The exception to this was the experiments with Mn\({}^{+2}\), which was tested at a final concentration of 20 mmol\(\cdot\)L\({}^{-1}\) and pre-incubated for 40 min. Appropriate controls were included for all the experiments, and the average values are reported as relative activity (%). The amino acids l-cysteine and l-tryptophan and the ion Mn\({}^{2+}\) interfered with the quantification of the reducing sugars by the DNS assay by 20% and 40%, respectively, which were corrected to obtain the final value of xylanase activity.