Lactonase activity of α-carbonic anhydrases allows identification of novel inhibitors.

Lactones, a diverse and abundant class of molecules found in nature, exhibit a wide range of bioactivities, including anti-inflammatory, anticancer, and antibacterial effects. Among them, acyl homoserine lactones (AHSLs) play a crucial role in quorum sensing, influencing bacterial pathogenicity and biofilm formation in Gram-negative bacteria. Paraoxonases (PONs), calcium-containing enzymes known for their lactonase activity, have been shown to hydrolyze AHSLs and reduce the biofilm formation of several pathogenic bacteria. In this study, we explored the potential lactonase activity of a class of zinc(II) enzymes, the carbonic anhydrases (CAs), aiming to uncover new insights into their catalytic versatility. Using LC-MS and MS/MS analyses, we investigated the lactonase activity of CAs and assessed several lactones through a stopped-flow kinetic assay as substrates/inhibitors. Our findings reveal that lactones are novel "prodrug" inhibitors of CAs, with lactones DHC and 6 showing the most promising inhibition constants (K_Is) in the low micromolar range against both human and bacterial isozymes.