Putative catalytic domain of uncharacterized bacterial polysaccharide deacetylases similar to bacterial PuuE allantoinases and Helicobacter pylori peptidoglycan deacetylase (HpPgdA)
This family contains many uncharacterized bacterial polysaccharide deacetylases (DCAs) that show high sequence similarity to the catalytic domain of bacterial PuuE allantoinases and Helicobacter pylori peptidoglycan deacetylase (HpPgdA). PuuE allantoinase appears to be metal-independent and specifically catalyzes the hydrolysis of (S)-allantoin into allantoic acid. Different from PuuE allantoinase, HpPgdA has the ability to bind a metal ion at the active site and is responsible for a peptidoglycan modification that counteracts the host immune response. Both PuuE allantoinase and HpPgdA function as homotetramers. The monomer is composed of a 7-stranded barrel with detectable sequence similarity to the 6-stranded barrel NodB homology domain of DCA-like proteins in the CE4 superfamily, which removes N-linked or O-linked acetyl groups from cell wall polysaccharides. In contrast to typical NodB-like DCAs, PuuE allantoinase and HpPgdA do not exhibit a solvent-accessible polysaccharide binding groove and might only bind a small molecule at the active site.
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