Structure and function of persulfide dioxygenase from Pseudomonas aeruginosa: Implications on H2S homeostasis and interplay with nitric oxide

Hydrogen sulfide is an important signaling molecule, beneficial at physiological concentrations but harmful at higher levels, due to which a tight control of its bioavailability is essential. Here, we investigated persulfide dioxygenase, an enzyme involved in H₂S catabolism, from the pathogen <i>Pseudomonas aeruginosa</i> (<i>Pa</i>PDO). Deletion of the gene <i>pdo</i> led to a 4-fold increase in H₂S concentration, confirming its physiological role. The recombinant enzyme was structurally characterized at 2.06 Å resolution and assigned to the metallo-β-lactamase superfamily. Compared with its human homolog, <i>Pa</i>PDO displayed a different dimerization area and a larger active site, suggesting different substrate preferences. Functionally, <i>Pa</i>PDO catalyzed glutathione persulfide dioxygenation with a high turnover rate, and its activity was enhanced by reduced glutathione. Interestingly, the results show that <i>Pa</i>PDO binds to nitric oxide, which reversibly inhibits its catalytic activity. These findings reveal a novel mechanism of crosstalk between hydrogen sulfide and nitric oxide signaling and provide insights into redox regulation in a multidrug-resistant pathogen.