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 is active with sugar beet arabinan and wheat arabinoxylan. It also exhibited activity against alpha-(1->5)-linked arabinobiose, arabinotriose, arabinotetraose, and arabinopentaose. Hydrolysis of terminal non-reducing alpha-L-arabinofuranoside residues in alpha-L-arabinosides. Completely inhibited by Hg(2+) and Cu(2+) ions, whereas 1 mM Zn(2+) inhibited activity by 51%. Optimum pH is 6. The enzyme retains full activity at pH values from 5.5 to 7.5. After exposure to pH 4.5, the activity is reduced by 40%, and no residual activity is detected at pH values below 4.5 or above 7.5. Optimum temperature is 45 degrees Celsius. The enzymatic activity decreases significantly at temperatures below 35 degrees Celsius and above 60 degrees Celsius, although considerable levels of activity are still detected at 20 and 70 degrees Celsius. Glycan metabolism; L-arabinan degradation. Homohexamer; trimer of dimers. Belongs to the glycosyl hydrolase 51 family.