Hydrolase involved in the degradation of the gum arabic arabinogalactan protein (AGP) and larch AGP. Catalyzes the release of 3-O-beta-L-arabinopyranosyl-L-arabinose (beta-L-Arap-(1->3)-L-Ara) from gum arabic AGP and larch AGP. Also cleaves a small amount of beta-L-Arap-(1->3)-L-Ara from sugar beet arabinan, but wheat AGP cannot be used as a substrate. Can also release 3-O-alpha-D-galactopyranosyl-L-arabinose (alpha-D-Galp-(1->3)-L-Ara) from gum arabic AGP, with low efficiency