Catalytic domain of bacterial PuuE allantoinases, Helicobacter pylori peptidoglycan deacetylase (HpPgdA), and similar proteins
This family is a member of the very large and functionally diverse carbohydrate esterase 4 (CE4) superfamily. It contains bacterial PuuE (purine utilization E) allantoinases, a peptidoglycan deacetylase from Helicobacter pylori (HpPgdA), Escherichia coli ArnD, and many uncharacterized homologs from all three kingdoms of life. 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 a homotetramer. The monomer is composed of a 7-stranded barrel with detectable sequence similarity to the 6-stranded barrel NodB homology domain of polysaccharide deacetylase (DCA)-like proteins in the CE4 superfamily, which removes N-linked or O-linked acetyl groups from cell wall polysaccharides. However, in contrast with the typical DCAs, PuuE allantoinase and HpPgdA might not exhibit a solvent-accessible polysaccharide binding groove and only recognize a small substrate molecule. ArnD catalyzes the deformylation of 4-deoxy-4-formamido-L-arabinose-phosphoundecaprenol to 4-amino-4-deoxy-L-arabinose-phosphoundecaprenol.
Comment:PuuE allantoinase appears to be metal-independent and acts on a small substrate molecule. Helicobacter pylori peptidoglycan deacetylase has the ability to bind a metal ion and a small substrate molecule at the active site.
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