Involved in the degradation of arabinan and is a key enzyme in the complete degradation of the plant cell wall. Catalyzes the cleavage of terminal alpha-L-arabinofuranosyl residues of arabinan present in the arabinofuranosyl polysaccharides or oligosaccharides. It cannot act on other arabinose-containing polysaccharides and arabinoxylo-oligosaccharides. It leaves most of the polymer intact, including most of the main-chain residues and the arabinose side chains. It acts preferentially on the linear alpha-(1->2)-linked arabinofuranobiosides and alpha-(1->3)-linked arabinofuranobiosides, and is much less effective on alpha-(1->5)-linked arabinofuranobiosides. It also hydrolyzes the terminal alpha-(1->3)-linked arabinofuranotriosides in preference to the alpha-(1->5)-linked arabinofuranotriosides. Hydrolysis of terminal non-reducing alpha-L-arabinofuranoside residues in alpha-L-arabinosides. Optimum pH is 5.5. The enzyme is slowly inactivated above pH 8.5 and below pH 5.5. Optimum temperature is 55 degrees Celsius. The enzyme is inactivated at temperatures above 45 degrees Celsius. Belongs to the glycosyl hydrolase 51 family.