The paraoxonase (PON) gene family of antioxidant enzymes includes three known members located adjacent to each other on chromosome 7. Paraoxonase/lactonase 3 (PON3) is a 354 amino acid, 39.6 kDa protein that is secreted into the bloodstream and associates with high-density lipoprotein (HDL). PON3 has lactonase activity (EC 3.1.1) and rapidly hydrolyzes lactones. PON3 exhibits no paraoxonase and very limited arylesterase activities. PON3 is an important antioxidant and can inhibit the oxidation of low-density lipoprotein (LDL), a function that may slow the initiation and progression of atherosclerosis.
