Catalytic NodB homology domain of Clostridium thermocellum acetylxylan esterase and its bacterial homologs. This family is represented by Clostridium thermocellum acetylxylan esterase (CtAXE, EC 3.1.1.72), a member of the carbohydrate esterase 4 (CE4) superfamily. CtAXE deacetylates O-acetylated xylan, a key component of plant cell walls. It shows no detectable activity on generic esterase substrates including para-nitrophenyl acetate. It is specific for sugar-based substrates and will precipitate acetylxylan, as a consequence of deacetylation. CtAXE is a monomeric protein containing a catalytic NodB homology domain with the same overall topology and a deformed (beta/alpha)8 barrel fold as other CE4 esterases. However, due to differences in the topography of the substrate-binding groove, the chemistry of the active center, and metal ion coordination, CtAXE has different metal ion preference and lacks activity on N-acetyl substrates. It is significantly activated by Co2+. Moreover, CtAXE displays distinctly different ligand coordination to the metal ion, utilizing an aspartate, a histidine, and four water molecules, as opposed to the conserved His-His-Asp zinc-binding triad of other CE4 esterases.

Catalytic NodB homology domain of rhizobial NodB-like proteins. This family belongs to the large and functionally diverse carbohydrate esterase 4 (CE4) superfamily, whose members show strong sequence similarity with some variability due to their distinct carbohydrate substrates. It includes many rhizobial NodB chitooligosaccharide N-deacetylase (EC 3.5.1.-)-like proteins, mainly from bacteria and eukaryotes, such as 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. All members of this family contain a catalytic NodB homology domain with the same overall topology and a deformed (beta/alpha)8 barrel fold with 6- or 7 strands. Their catalytic activity is dependent on the presence of a divalent cation, preferably cobalt or zinc, and they employ 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. Several family members show diversity both in metal ion specificities and in the residues that coordinate the metal.

Catalytic NodB homology domain of Streptococcus pneumoniae peptidoglycan deacetylase PgdA, Bacillus subtilis BsYjeA protein, and their bacterial homologs. This family is represented by Streptococcus pneumoniae peptidoglycan GlcNAc deacetylase (SpPgdA), a member of the carbohydrate esterase 4 (CE4) superfamily. SpPgdA protects gram-positive bacterial cell wall from host lysozymes by deacetylating peptidoglycan N-acetylglucosamine (GlcNAc) residues. It consists of three separate domains: N-terminal, middle and C-terminal (catalytic) domains. The catalytic NodB homology domain is similar to the deformed (beta/alpha)8 barrel fold adopted by other CE4 esterases, which harbors a mononuclear metalloenzyme employing a conserved His-His-Asp zinc-binding triad closely associated with conserved catalytic base (aspartic acid) and acid (histidine) to carry out acid/base catalysis. The enzyme is able to accept GlcNAc3 as a substrate, with the N-acetyl of the middle sugar being removed by the enzyme. This family also includes Bacillus subtilis BsYjeA protein encoded by the yjeA gene, which is one of the six polysaccharide deacetylase gene homologs (pdaA, pdaB/ybaN, yheN, yjeA, yxkH and ylxY) in the Bacillus subtilis genome. Although homology comparison shows that the BsYjeA protein contains a polysaccharide deacetylase domain, and was predicted to be a membrane-bound xylanase or a membrane-bound chitooligosaccharide deacetylase, more recent research indicates BsYjeA might be a novel non-specific secretory endonuclease which creates random nicks progressively on the two strands of dsDNA, resulting in highly distinguishable intermediates/products very different in chemical and physical compositions over time. In addition, BsYjeA shares several enzymatic properties with the well-understood DNase I endonuclease. Both enzymes are active on ssDNA and dsDNA, both generate random nicks, and both require Mg2+ or Mn2+ for hydrolytic activity.

Catalytic NodB homology domain of uncharacterized bacterial glycosyl transferase, group 2-like family proteins. This family includes many uncharacterized bacterial proteins containing an N-terminal GH18 (glycosyl hydrolase, family 18) domain, a middle NodB-like homology domain, and a C-terminal GT2-like (glycosyl transferase group 2) domain. Although their biological function is unknown, members in this family contain a middle NodB homology domain that is similar to the catalytic domain of Streptococcus pneumoniae polysaccharide deacetylase PgdA (SpPgdA), an extracellular metal-dependent polysaccharide deacetylase with de-N-acetylase activity toward a hexamer of chitooligosaccharide N-acetylglucosamine, but not shorter chitooligosaccharides or a synthetic peptidoglycan tetrasaccharide. Like SpPgdA, this family is a member of the carbohydrate esterase 4 (CE4) superfamily. The presence of three domains suggests that members of this family may be multifunctional.

Peptidoglycan/xylan/chitin deacetylase, PgdA/CDA1 family [Carbohydrate transport and metabolism, Cell wall/membrane/envelope biogenesis].

Crystalstructure of the Xyl-CE4 domain of a multidomain xylanase from the hindgut metagenome of Trinervitermes trinervoides [uncultured bacterium]

ChainA, Glycoside Hydrolase, Family 11:clostridium Cellulosome Enzyme, Dockerin Type I:polysaccharide [Acetivibrio thermocellus],2C79_A Chain A, GLYCOSIDE HYDROLASE, FAMILY 11:CLOSTRIDIUM CELLULOSOME ENZYME, DOCKERIN TYPE I:POLYSACCHARIDE [Acetivibrio thermocellus]

Structureof Streptococcus pneumoniae peptidoglycan deacetylase (SpPgdA) [Streptococcus pneumoniae R6]

Crystalstructure of the Bc1960 peptidoglycan N-acetylglucosamine deacetylase in complex with 4-naphthalen-1-yl-~{N}-oxidanyl-benzamide [Bacillus cereus ATCC 14579]

Structureof Streptococcus pneumoniae peptidoglycan deacetylase (SpPgdA) D 275 N Mutant. [Streptococcus pneumoniae R6]

Bifunctional xylanase/deacetylase OS=Pseudobutyrivibrio xylanivorans OX=185007 GN=xyn11A PE=1 SV=2

Peptidoglycan-N-acetylglucosamine deacetylase PgdA OS=Listeria monocytogenes serotype 1/2a (strain EGD / Mackaness) OX=1334565 GN=pgdA PE=1 SV=1

Peptidoglycan-N-acetylglucosamine deacetylase PgdA OS=Listeria monocytogenes serovar 1/2a (strain ATCC BAA-679 / EGD-e) OX=169963 GN=pgdA PE=1 SV=1

Peptidoglycan-N-acetylglucosamine deacetylase PgdA OS=Listeria monocytogenes serotype 1/2a (strain 10403S) OX=393133 GN=pgdA PE=2 SV=1

Peptidoglycan-N-acetylglucosamine deacetylase OS=Streptococcus pneumoniae (strain ATCC BAA-255 / R6) OX=171101 GN=pgdA PE=1 SV=1