N-acyl homoserine lactones (AHLs) acted as the key quorum-sensing (QS) signal molecules in gram-negative bacteria,which coordinate gene expression and then activate different processes like biofilm formation and virulence factor production in some bacterial pathogens.Quorum quenching,inactivation of the signaling molecule by enzymatic degradation or modification,would inhibit the processes of quorum-sensing rather than kill the pathogens and represents an promising anti-pathogenic strategy to control bacterial infections.In this study,an AHL lactonase (named AiiK),being identified,cloned and expressed from Kurthia huakuii LAM0618,which has a broad substrate spectrum and a efficient degradation of the AHL compounds with or without a substitution of oxo-group at the C-3 position.High-performance liquid chromatography (HPLC) analyses showed that AiiK functioned as an AHL lactonase to hydrolyze the ester bond of the homoserine lactone ring of AHLs.The enzyme,belonging to the metallo-β-lactamase superfamily,shares 26 % and 42% identity with the AHL lactonase AiiA and AiiB,respectively.The overall catalytic efficiency of AiiK for C10-HSL is 3.9 s-1·mM-1 and 4 μg/mL of AiiK could degrade 97% of C10-HSL (50 μM) in 30 min at 25 ℃.In addition,the results showed that AiiK exhibited great resistance to α-chymotrypsin,trypsin or protease K.Furthermore,AiiK significantly inhibited the biofilm formation and attenuated pyocyanin production of Pseudomonas aeruginosa PAO1,which suggests that AiiK has a promising prospect to be applied as a anti-pathogenic agent.