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.

polysaccharide deacetylase family sporulation protein PdaB. This model describes the YbaN protein family, also called PdaB and SpoVIE, of Gram-positive bacteria. Although ybaN null mutants have only a mild sporulation defect, ybaN/ytrI double mutants show drastically reducted sporulation efficiencies. This synthetic defect suggests the role of this sigmaE-controlled gene in sporulation had been masked by functional redundancy. Members of this family are homologous to a characterized polysaccharide deacetylase; the exact function this protein family is unknown. [Cellular processes, Sporulation and germination]

Putative catalytic NodB homology domain of uncharacterized protein YlxY from Bacillus subtilis and its bacterial homologs. The Bacillus subtilis genome contains six polysaccharide deacetylase gene homologs: pdaA, pdaB (previously known as ybaN), yheN, yjeA, yxkH and ylxY. This family is represented by Bacillus subtilis putative polysaccharide deacetylase BsYlxY, encoded by the ylxY gene, which is a member of the carbohydrate esterase 4 (CE4) superfamily. Although its biological function still remains unknown, BsYlxY shows high sequence homology to the catalytic domain of Bacillus subtilis pdaB gene encoding a putative polysaccharide deacetylase (BsPdaB), which is essential for the maintenance of spores after the late stage of sporulation and is highly conserved in spore-forming bacteria. However, disruption of the ylxY gene in B. subtilis did not cause any sporulation defect. Moreover, the Asp residue in the classical His-His-Asp zinc-binding motif of CE4 esterases is mutated to a Val residue in this family. Other catalytically relevant residues of CE4 esterases are also not conserved, which suggest that members of this family may be inactive.

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 Streptococcus mutans polysaccharide deacetylase PgdA, Bacillus subtilis YheN, and similar proteins. This family is represented by a putative polysaccharide deacetylase PgdA from the oral pathogen Streptococcus mutans (SmPgdA) and Bacillus subtilis YheN (BsYheN), which are members of the carbohydrate esterase 4 (CE4) superfamily. SmPgdA is an extracellular metal-dependent polysaccharide deacetylase with a typical CE4 fold, with metal bound to a His-His-Asp triad. It possesses de-N-acetylase activity toward a hexamer of chitooligosaccharide N-acetylglucosamine, but not shorter chitooligosaccharides or a synthetic peptidoglycan tetrasaccharide. SmPgdA plays a role in tuning cell surface properties and in interactions with (salivary) agglutinin, an essential component of the innate immune system, most likely through deacetylation of an as-yet-unidentified polysaccharide. SmPgdA shows significant homology to the catalytic domains of peptidoglycan deacetylases from Streptococcus pneumoniae (SpPgdA) and Listeria monocytogenes (LmPgdA), both of which are involved in the bacterial defense mechanism against human mucosal lysozyme. The Bacillus subtilis genome contains six polysaccharide deacetylase gene homologs: pdaA, pdaB (previously known as ybaN), yheN, yjeA, yxkH and ylxY. The biological function of BsYheN is still unknown. This family also includes many uncharacterized polysaccharide deacetylases mainly found in bacteria.

ChainA, Predicted xylanase/chitin deacetylase [Caldanaerobacter subterraneus subsp. tengcongensis MB4]

ChainA, Putative polysaccharide deacetylase [Bacillus anthracis]

Crystalstructure of a BA3943 mutant,a CE4 family pseudoenzyme with restored enzymatic activity. [Bacillus anthracis]

Crystalstructure of a BA3943 mutant,a CE4 family pseudoenzyme [Bacillus anthracis]

Structureof peptidoglycan deacetylase PdaC from Bacillus subtilis - mutant D285S [Bacillus subtilis subsp. subtilis str. 168],6H8N_B Structure of peptidoglycan deacetylase PdaC from Bacillus subtilis - mutant D285S [Bacillus subtilis subsp. subtilis str. 168]

Uncharacterized protein YlxY OS=Bacillus subtilis (strain 168) OX=224308 GN=ylxY PE=3 SV=2

Peptidoglycan-N-acetylmuramic acid deacetylase PdaC OS=Bacillus subtilis (strain 168) OX=224308 GN=pdaC PE=1 SV=1

Peptidoglycan-N-acetylglucosamine deacetylase BC_1960 OS=Bacillus cereus (strain ATCC 14579 / DSM 31 / CCUG 7414 / JCM 2152 / NBRC 15305 / NCIMB 9373 / NCTC 2599 / NRRL B-3711) OX=226900 GN=BC_1960 PE=1 SV=1

Probable polysaccharide deacetylase PdaB OS=Bacillus subtilis (strain 168) OX=224308 GN=pdaB PE=3 SV=2

Peptidoglycan-N-acetylglucosamine deacetylase BC_3618 OS=Bacillus cereus (strain ATCC 14579 / DSM 31 / CCUG 7414 / JCM 2152 / NBRC 15305 / NCIMB 9373 / NCTC 2599 / NRRL B-3711) OX=226900 GN=BC_3618 PE=1 SV=1