Involved in the degradation of arabinan and is a key enzyme in the complete degradation of the plant cell wall. Catalyzes the internal cleavage of alpha-(1->5)-L-arabinofuranosyl residues in different arabinan-containing polysaccharides, and releases arabinotriose and arabinobiose as end products. It acts on branched arabinan (from sugar beet), but more slowly when compared to linear or debranched arabinan. Endohydrolysis of (1->5)-alpha-arabinofuranosidic linkages in (1->5)-arabinans. Binds 1 Ca(2+) ion per subunit. Optimum pH is 6.0. It retains more than 75% activity over a pH range from 4 to 7. Optimum temperature is 73 degrees Celsius. It is fully heat-stable (up to 10 hours) and retains activity at temperatures up to 90 degrees Celsius. The enzyme loses its activity only after 90 minutes when incubated at 95 degrees Celsius. Glycan metabolism; L-arabinan degradation. Monomer. Although it functions as an extracellular endo-alpha-(1->5)-L-arabinanase, its sequence is quite divergent from the B.subtilis enzyme. Belongs to the glycosyl hydrolase 43 family.