Capable of hydrolyzing lactones and a number of aromatic carboxylic acid esters. Has antioxidant activity. Is not associated with high density lipoprotein. Prevents LDL lipid peroxidation, reverses the oxidation of mildly oxidized LDL, and inhibits the ability of MM-LDL to induce monocyte chemotaxis. a phenyl acetate + H2O = a phenol + acetate + H(+) an N-acyl-L-homoserine lactone + H2O = an N-acyl-L-homoserine + H(+) Binds 2 calcium ions per subunit. Homotrimer. Widely expressed with highest expression in liver, lung, placenta, testis and heart. The signal sequence is not cleaved. Ser-311 is associated with an increased risk of cornary heart disease. Belongs to the paraoxonase family.