Involved in the degradation of xylan and is a key enzyme in the complete degradation of the plant cell wall. It has a specific arabinofuranose-debranching activity on xylan from gramineae. Acts synergistically with the xylanases and binds specifically to xylan. From small arabinoxylo-oligosides (ranging from arabinoxylotriose to arabinoxylohexaose), it liberates arabinose and, after prolonged incubation, the purified enzyme exhibits some xylanolytic activity as well. Hydrolysis of terminal non-reducing alpha-L-arabinofuranoside residues in alpha-L-arabinosides. Optimum pH is 6. Optimum temperature is 55 degrees Celsius. Glycan degradation; xylan degradation. These dual activities might be explained by a rotation about the alpha-(1->3)-glycosidic bond of the arabinofuranose group to the xylose moiety of xylan, which produces a bond conformation resembling that of a beta-(1->4) bond found in xylosides. Thus a single catalytic site could perform the double activity (PubMed:9148759). Belongs to the glycosyl hydrolase 62 family.