Lipoprotein-associated phospholipase A2 (Lp-PLA2) also known as platelet-activating factor acetylhydrolase (PAF-AH) is a phospholipase A2 enzyme. It is one of several PAF acetylhydrolases that catalyzes the degradation of PAF to inactive products by hydrolysis of the acetyl group at the sn-2 position, producing the biologically inactive products LYSO-PAF and acetate. It is an enzyme produced by inflammatory cells and hydrolyzes oxidized phospholipids in LDL. In the blood Lp-PLA2 travels mainly with low-density lipoprotein (LDL). Less than 20% is associated with high-density lipoprotein HDL. HDL-associated Lp-PLA2 may substantially contribute to the HDL antiatherogenic activities. In human atherosclerotic lesions, 2 main sources of Lp-PLA2 can be identified, including that which is brought into the intima bound to LDL (from the circulation), and that which is synthesized de novo by plaque inflammatory cells (macrophages, T cells, mast cells). It is used as a marker for cardiac disease. Lp-PLA2 levels are positively correlated with increased risk of developing coronary heart disease and stroke.