An α/β-Hydrolase Fold Subfamily Comprising <i>Pseudomonas</i> Quinolone Signal-Cleaving Dioxygenases

Abstract

Functional annotation of protein sequences is a major requirement for the investigation of metabolic pathways and the identification of sought-after biocatalysts. To identify heterocyclic ring-cleaving dioxygenases within the huge superfamily of α/β-hydrolase fold proteins, we defined search and validation criteria for the primarily motif-based identification of 3-hydroxy-4(1 H )-quinolone 2,4-dioxygenases (HQD). HQDs are key enzymes for the inactivation of metabolites, which can have signaling, antimicrobial, or cytotoxic functions. The HQD candidates detected in this study occur particularly in environmental and plant-associated microorganisms. Because HQDs active toward the Pseudomonas quinolone signal (PQS) likely contribute to interactions within microbial communities and modulate the virulence of Pseudomonas aeruginosa , we analyzed the catalytic properties of a PQS-cleaving subset of HQDs and specified characteristics to identify PQS-cleaving dioxygenases within the HQD family.