Involved in plant cell wall degradation in cooperation with cellulosome. Hydrolyzes both p-nitrophenyl-alpha-L-arabinopyranoside (pNPAp) and p-nitrophenyl-beta-D-galactopyranoside (pNPGp), with higher activity for pNPAp. Shows hydrolysis activity against p-nitrophenyl-beta-D-fucopyranoside (pNPFp), but not against p-nitrophenyl-alpha-L-arabinofuranoside (pNPAf), o-nitrophenyl-beta-D-galactopyranoside (oNPGp), p-nitrophenyl-beta-D-xylopyranoside (pNPXp), p-nitrophenyl-beta-D-glucopyranoside (pNPGLp), p-nitrophenyl-beta-D-cellobiopyranoside (pNPCp), p-nitrophenyl-beta-lactopyranoside (pNPLp) or p-nitrophenyl-alpha-galactopyranoside (pNPalphaGp). No detectable activity against arabinan or arabinoxylan, but activity against arabinogalactan can be detected. Increases degradation activity of alpha-L-arabinofuranosidase (ArfA) and endo-1,4-beta-xylanase (XynA) when corn fiber gum and corn stem powder are used as substrates. Hydrolysis of terminal non-reducing beta-D-galactose residues in beta-D-galactosides. Inhibited by Cu(2+), Hg(2+) and Zn(2+). No effect with Ca(2+), Mg(2+), Mn(2+) or excess EDTA (10 mM). Optimum pH is 6.0 for activities against both pNPAp and pNPGp. Stable in the range of pH 6.0-8.0. Optimum temperature is 30-40 degrees Celsius for activities against both pNPAp and pNPGp when incubated 10 minutes at pH 6.0. Both activities completely lost after heating at 50 degrees Celsius for 20 minutes. Dimer. Belongs to the glycosyl hydrolase 42 family.