Enzymes active on glycosidic bonds are defined according to the stereochemistry
of both substrates and products of the reactions they catalyse. The CAZy classification further
assigns these enzymes into sequence-based families sharing a common stereochemistry for
substrates (either α- or β-) and products, i.e. inverting or retaining mechanism. Here we describe
the N-acetylgalactosaminidases AmGH109A and AmGH109B from the human gut symbiont
Akkermansia muciniphila. Notably, AmGH109A displays α-retaining and β-inverting
N-acetylgalactosaminidase activities with comparable efficiencies on natural disaccharides. This
dual specificity could provide an advantage in targeting a broader range of host-derived glycans.
We rationalise this discovery through bioinformatics, structural, mutational, and computational
studies, unveiling a histidine residing in a conserved GGHGG motif as the elusive catalytic acidbase of the GH109 family.
- Glycoside hydrolase
- Human gut microbiota
- Inverting mechanism
- MD simulations
, Shuoker, B., Chaberski, E. K., Kunstmann, R. S., Fredslund, F., Peters, G. H. J.
, Nordberg Karlsson, E., Welner, D. H., & Abou Hachem, M.
(2020). The catalytic acid-base in GH109 resides in a conserved GGHGG loop and allows for comparable α-retaining and β-inverting activity in an N-acetylgalactosaminidase from Akkermansia muciniphila
. A C S Catalysis
, 3809-3819. https://doi.org/10.26434/chemrxiv.9989102.v1