Glycoside hydrolases (GHs, EC 3.2.1.-) form a widespread group of enzymes that
hydrolyze the glycoside bond between monosaccharide units or between a
carbohydrate and an aglycone moiety. GHs can act specifically as exo-cleaving
enzymes to remove the sugar units from the ends of chains and release small
sugar products, or endo-cleaving enzymes to act within the polysaccharide
chain and produce oligosaccharides. Family 84 glycoside hydrolases (GH84)
cleave the glycosidic linkage of N-acetylglucosaminides by a two-step
catalytic mechanism that involves a pair of aspartate residues as catalytic
residues, D1 as the polarizing residue and Asp175 as the general acid/base
catalyst [E1,E2]. The GH84 catalytic domain is found both in eukaryotic and
prokaryotic proteins:
Mammalian O-GlcNAcase (OGA).
Bacterial O-GlcNAcase (OGA).
Clostridium perfringens NagH, NagI, NagJ and NagK proteins, act as β-N-
acetyl-D-glucosaminidases able to hydrolyze N- and O-glycan motifs. In
addition to the GH84 catalytic modules, all four enzymes contain a
combination of ancillary modules, such as family 32 carbohydrate-binding
(CBM32s), found-in-various-architectures (FIVAR), fibronectin-like type III
(FN3) (see <PDOC50853>), cohesin (X82) and/or Dockerin (Doc) (see
<PDOC51766>) modules, as well as uncharacterized modules.
The GH84 catalytic domain consists of a classic (β/α)8-barrel (eight-stranded parallel β-sheet core mainly surrounded by eight α-helices),
which forms a deep pocket for GlcNAc binding and hydrolysis (see <PDB:5TKE>)
[1,2,3,4,5,6,7].
The profile we developed covers the whole GH84 catalytic domain.
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