**2. Lipoprotein-associated phospholipase A2: structure and biology**

Lipoprotein-associated phospholipase A2 (Lp-PLA2), also known as platelet-activating factor acetylhydrolase (PAF-AH), belongs to the phospholipase A2 superfamily [1,2]. This Ca2+ independent phospholipase is encoded by *PLA2G7* gene that consists of 12 exons and 11 introns located on chromosome 6p21.2 to 12 [3,4]. Lp-PLA2 is protein of 45,4 kDa that consists of 441 amino acid residues [5]. The major sources of Lp-PLA2 in plasma are T lymphocytes, mono‐ cytes/macrophages, activated bone marrow-derived mast cells, and liver cells [6-8]. The secreted Lp-PLA2, circulates in plasma in active form. It predominantly binds to LDLs, and in a much smaller extent to HDLs, Lp(a), lipoprotein remnants, and platelet-borne microparticles [6,9-12]. Indeed, Lp-PLA2 is highly associated with the smallest LDL and HDL subclasses [13] and with electronegative LDL, which overlaps with small dense LDL [14]. Lp-PLA2 bound to HDL has a much lower specific activity compared to when bound to LDL [10]. Different distribution of Lp-PLA2 in various plasma lipoproteins affects its functions.

Lp-PLA2 catalyzes hydrolysis of the acetyl group at sn-2 position of PAF to generate lyso-PAF and acetate [15]. On the other side, Lp-PLA2 cleaves oxidatively modified lipoproteins from the sn-2 position of the apoB100-containing lipoproteins into oxidized nonesterified fatty acids (oxFFAs) and lysophosphatidylcholine.
