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 different hemicellulosic homopolysaccharides (branched and debranched arabinans). It acts preferentially on arabinotriose, arabinobiose and linear alpha-(1->5)-L-arabinan, and is much less effective on branched sugar beet arabinan. Hydrolysis of terminal non-reducing alpha-L-arabinofuranoside residues in alpha-L-arabinosides. Optimum pH is 8. Optimum temperature is 50 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 (Probable). Cells lacking this gene retain 38% of arabinofuranosidase activity, and the double mutant abfA/abf2 is inactive. Belongs to the glycosyl hydrolase 51 family.