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Catalytic NodB homology domain of the carbohydrate esterase 4 superfamily The carbohydrate esterase 4 (CE4) superfamily mainly includes chitin deacetylases (EC 3.5.1.41), bacterial peptidoglycan N-acetylglucosamine deacetylases (EC 3.5.1.-), and acetylxylan esterases (EC 3.1.1.72), which catalyze the N- or O-deacetylation of substrates such as acetylated chitin, peptidoglycan, and acetylated xylan, respectively. Members in this superfamily contain a NodB homology domain that adopts a deformed (beta/alpha)8 barrel fold, which encompasses a mononuclear metalloenzyme employing a conserved His-His-Asp zinc-binding triad, closely associated with the conserved catalytic base (aspartic acid) and acid (histidine) to carry out acid/base catalysis. The NodB homology domain of CE4 superfamily is remotely related to the 7-stranded beta/alpha barrel catalytic domain of the superfamily consisting of family 38 glycoside hydrolases (GH38), family 57 heat stable retaining glycoside hydrolases (GH57), lactam utilization protein LamB/YcsF family proteins, and YdjC-family proteins.
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