Cloning, purification and biochemical characterisation of a GH35 beta-1,3/beta-1,6-galactosidase from the mucin-degrading gut bacterium Akkermansia muciniphila

A putative GH35 beta-galactosidase gene from the mucin-degrading bacterium Akkermansia muciniphila was successfully cloned and further investigated. The recombinant enzyme with the molecular mass of 74 kDa was purified to homogeneity and biochemically characterised. The optimum temperature of the enzyme was 42 A degrees C, and the optimum pH was determined to be pH 3.5. The addition of sodium dodecyl sulphate (SDS) reduced the enzyme's activity significantly. The addition of Mg2+-ions decreased the activity of the beta-galactosidase, whereas other metal ions or EDTA showed no inhibitory effect. The enzyme catalysed the hydrolysis of beta 1,3- and beta 1,6- linked galactose residues from various substrates, whereas only negligible amounts of beta 1,4-galactose were hydrolysed. The present study describes the first functional characterisation of a beta-galactosidase from this human gut symbiont.