Signal interference effect of human paraoxonase 1 using as substrates N-hexanoyl-L-homoserine lactone and N-3-oxo-octanoyl-L-homoserine lactone on growth of pathogenic bacteria

Paraoxonase 1 (PON1) is human lactonase orginally described as enzyme that is capable of hydrolyzing organophosphates. The hypothesis suggested that this enzyme may also participate in attenuation of bacterial virulence through interfering with quorum sensing (QS). Recently, PON1 was shown to hydrolyze over 30 lactones. In the present study, human PON1 (hPON1) was purified using ammonium sulphate precipitation and Sepharose-4B-L-tyrosine-1-naphthylamine hydrophobic interaction chromatography. The purified enzyme had a specific activity of 11.89 U/mg protein and catalyzed the hydrolysis of N-hexanoyl-L-homoserine lactone (C10HSL) and N-3-oxo-octanoyl-L-homoserine lactone (3OC8HSL). The hydrolysis reaction was analyzed with HPLC. The K (M) values for hPON1 using 3OC8HSL or C10HSL as subtrate were calculated as 2.71 and 0.80 mM and V (max) values were detected as 1428.57 and 45.24 A mu moles mg(-1) min(-1), respectively. Also, effect of hPON1 on growth of pathogenic bacterial strains using the signal lactone molecules was investigated by microtiter plate assay. Our results demonstrated that hPON1 was responsible for inhibition of QS system by hydrolyzing of signal molecules and effecting bacterial growth.