-!- Acts on organophosphorus compounds (such as paraoxon) including esters of phosphonic and phosphinic acids. -!- Inhibited by chelating agents. -!- Previously regarded as identical with EC 3.1.1.2.

-!- Acyl-homoserine lactones (AHLs) are produced by a number of bacterial species and are used by them to regulate the expression of virulence genes in a process known as quorum-sensing. -!- Each bacterial cell has a basal level of AHL and, once the population density reaches a critical level, it triggers AHL-signaling which, in turn, initiates the expression of particular virulence genes. -!- Plants or animals capable of degrading AHLs would have a therapeutic advantage in avoiding bacterial infection as they could prevent AHL- signaling and the expression of virulence genes in quorum-sensing bacteria. -!- N-(3-oxohexanoyl)-L-homoserine lactone, N-(3-oxododecanoyl)-L- homoserine lactone, N-butanoyl-L-homoserine lactone and N-(3-oxooctanoyl)-L-homoserine lactone can act as substrates.

-!- Acts on many phenolic esters. -!- It is likely that the three forms of human paraoxonase are lactonases rather than aromatic esterases. -!- The natural substrates of the paraoxonases are lactones, with (+-)-5- hydroxy-6E,8Z,11Z,4Z-eicostetraenoic-acid 1,5-lactone being the best substrate.