Beta-L-arabinobiosidase that removes L-arabinofuranose-beta-1,2-L-arabinofuranose disaccharide from various substrates such as carrot extensin and potato lectin. Also acts on L-arabinofuranose (Ara)-beta-1,2-Ara-beta-1,2-Ara-beta-Hyp (Ara(3)-Hyp) but not on Ara-beta-1,3-Ara-beta-1,2-Ara-beta-1,2-Ara-beta--Hyp (Ara(4)-Hyp) or Ara-beta-1,2-Ara-beta-Hyp (Ara(2)-Hyp), suggesting a specificity for unmodified Ara(3)-Hyp substrate. In the presence of 1-alkanols, shows transglycosylation activity, retaining the anomeric configuration of the arabinofuranose residue. 4-O-(beta-L-arabinofuranosyl-(1->2)-beta-L-arabinofuranosyl-(1->2)-beta-L-arabinofuranosyl)-(2S,4S)-4-hydroxyproline + H2O = 4-O-(beta-L-arabinofuranosyl)-(2S,4S)-4-hydroxyproline + beta-L-arabinofuranosyl-(1->2)-beta-L-arabinofuranose Optimum pH is 5.5-6.0. Optimum temperature is 30 degrees Celsius. Predicted to be exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Belongs to the glycosyl hydrolase 121 family.