Phospholipase A2

Phospholipase A2 (PLA2 catalyzes the hydrolysis of the sn-2 position of membrans glyerophospholipids to liberate arachidonic acid (AA), a precursor of eicosanoids including prostaglandins (PGs) and leukotrienes (LTs). The same reaction also produces lysophosholipids, which represent another class of lipid mediators. So far, at least 19 enzymes that posses PLA2 activity have been identified in mammals. The secretory PLA2 (sPLA2) family, in which 10 isozymes have been identified, consists of low-molecular-weight, Ca2+-requring, secretory enzymes that have been implicated in a number of biological processes, such as modification of cicosanoid generation, inflammation, host defense, and atheroselecrosis. The cytosolic PLA2 (cPLA2) family consists of 3 enzymes, among which cPLA2α plays an essential role in the initiation of AA metabolism. Intracellular activation of cPLA2α is tightly regulated by Ca2+ and phosphorylation. The Ca2+, independent PLA2 (iPLA2) family contains 2 enzymes and may play a major role in membrane phospholipid remodeling. The platelet-activating factor (PAF) acetylhydrolase (PAF-AH) family represents a unique group of PLA2 that contains 4 enzymes exhibiting unusual substrate specificity toward PAF and/or oxidized phospholipids. In this review, we will overview current understanding of the properties and functions of each enzyme belonging to the sPLA2, cPLA2, and iPLA2, families, which have been implicated in signal transduction.