Reaction: Hydrolysis of (1→6)-β-D-galactosidic linkages in arabinogalactan proteins and (1→3):(1→6)-β-galactans to yield (1→6)-β-galactobiose as the final product.
Other name(s): exo-β-1,6-galactobiohydrolase; 1,6Gal (gene name)
Systematic name: exo-β-(1→6)-galactobiohydrolase (non-reducing end)
Comments: The enzyme, characterized from the bacterium Bifidobacterium longum, specifically hydrolyses (1→6)-β-galactobiose from the non-reducing terminal of (1→6)-β-D-galactooligosaccharides with a degree of polymerization (DP) of 3 or higher, using an exo mode of action. The enzyme cannot hydrolyse α-L-arabinofuranosylated (1→6)-β-galactans (as found in arabinogalactans) and does not act on (1→3)-β-D- or (1→4)-β-D-galactans. cf. EC 126.96.36.199, galactan endo-1,6-β-galactosidase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
1. Fujita, K., Sakamoto, A., Kaneko, S., Kotake, T., Tsumuraya, Y. and Kitahara, K. Degradative enzymes for type II arabinogalactan side chains in Bifidobacterium longum subsp. longum. Appl. Microbiol. Biotechnol. 103 (2019) 1299-1310. [PMID: 30564851]