PaaI_thioesterase is a tetrameric acyl-CoA thioesterase with a hot dog fold and one of several proteins responsible for phenylacetic acid (PA) degradation in bacteria. Although orthologs of PaaI exist in archaea and eukaryotes, their function has not been determined. Sequence similarity between PaaI, E. coli medium chain acyl-CoA thioesterase II, and human thioesterase III suggests they all belong to the same thioesterase superfamily. The conserved fold present in these thioesterases is referred to as an asymmetric hot dog fold, similar to those of 4-hydroxybenzoyl-CoA thioesterase (4HBT) and the beta-hydroxydecanoyl-ACP dehydratases (FabA/FabZ).
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