Involved in depolymerization of xylan, a major component of the lignocellulosic substrates. Acts as an endo-xylanase that efficiently hydrolyzes the beta-1,4 glycosidic linkages between the xylopyranosyl residues in the main chain of the polymer, leading to the degradation of xylan into short oligosaccharides. Shows high activity toward branched xylans from both softwoods (arabinoxylans) and hardwoods (glucuronoxylans), showing the highest activity on beechwood xylan. Also hydrolyzes long xylooligosaccharides (with a degree of polymerization of greater than or equal to 5), while oligomers shorter than xylotetraose are not degraded. Is not active on carboxymethyl cellulose (CMC), Avicel, starch, polygalacturonic acid, laminarin, pectin, beta-D-barley glucan, or lichenan. Endohydrolysis of (1->4)-beta-D-xylosidic linkages in xylans. Optimum pH is 6.5. Optimum temperature is 50 degrees Celsius. Retains about 80% of the activity after incubation for 2 hours at 50 degrees Celsius, but is rapidly inactivated at higher temperatures. Glycan degradation; xylan degradation. This enzyme liberates reducing sugars from elemental chlorine free (ECF) and totally chlorine free (TCF) bleached pulps from eucalyptus, sisal, and flax, which makes it a good candidate for the enzymatic-assisted production of high-cellulose-content pulps from paper-grade pulps. Is dependent on P.barcinonensis lipoprotein LppX for its expression in an active form. Belongs to the glycosyl hydrolase 11 (cellulase G) family.