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 in different hemicellulosic homopolysaccharides (branched and debranched arabinans) and heteropolysaccharides (arabinoxylans). It is able to hydrolyze the alpha-(1->5)-glycosidic linkages of linear alpha-(1->5)-L-arabinan (debranched), sugar beet arabinan (branched) and wheat arabinoxylan. Moreover, it displays higher activity towards branched arabinan, a molecule comprising a backbone of alpha-(1->5)-linked L-arabinofuranosyl residues decorated with alpha-(1->2)-, and alpha-(1->3)-linked L-arabinofuranosyl units, than towards debranched arabinan. In addition, arabinoxylan, which has L-arabinofuranose residues attached to the main chain by alpha-(1->2)- and/or alpha-(1->3)-glycosidic linkages, is preferred to linear alpha-(1->5)-L-arabinan. Hydrolysis of terminal non-reducing alpha-L-arabinofuranoside residues in alpha-L-arabinosides. Optimum pH is 8. Optimum temperature is 60 degrees Celsius. Glycan metabolism; L-arabinan degradation. Homohexamer; trimer of dimers. Transcription is repressed by glucose and by the binding of AraR to the operon promoter. L-arabinose acts as an inducer by inhibiting the binding of AraR to the DNA, thus allowing expression of the gene. Cells lacking this gene retain 70% of arabinofuranosidase activity, and the double mutant abfA/abf2 is inactive. Belongs to the glycosyl hydrolase 51 family.