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-(1->5)-arabinofuranosyl bonds in small oligosaccharides as alpha-(1->5)-linked arabinobiose/arabinotriose, but does not display significant activity against linear non-substituted arabinan. It is also highly efficient in the cleavage of alpha-(1->3)-linked arabinoside of xylobiose and of the alpha-(1->3)-linked arabinoside decorations of polymeric wheat arabinoxylan. It exhibits very low activity against sugar beet arabinan. Hydrolysis of terminal non-reducing alpha-L-arabinofuranoside residues in alpha-L-arabinosides. Optimum pH is 6.0. Optimum temperature is 60 degrees Celsius. Glycan metabolism; L-arabinan degradation. Homohexamer; trimer of dimers. Belongs to the glycosyl hydrolase 51 family.