Properties of the Group IV phospholipase A2 family.

The Group IV phospholipase A2 family is comprised of six intracellular enzymes commonly called cytosolic phospholipase A2 (cPLA2) alpha, cPLA2beta, cPLA2gamma, cPLA2delta, cPLA2epsilon and cPLA2zeta. They are most homologous to phospholipase A and phospholipase B/lysophospholipases of filamentous fungi particularly in regions containing conserved residues involved in catalysis. However, a number of other serine acylhydrolases (patatin, Group VI PLA2s, Pseudomonas aeruginosa ExoU and NTE) contain the Ser/Asp catalytic dyad characteristic of Group IV PLA2s, and recent structural analysis of patatin has confirmed its structural similarity to cPLA2alpha. A characteristic of all these serine acylhydrolases is their ability to carry out multiple reactions to varying degrees (PLA2, PLA1, lysophospholipase and transacylase activities). cPLA2alpha, the most extensively studied Group IV PLA2, is widely expressed in mammalian cells and mediates the production of functionally diverse lipid products in response to extracellular stimuli. It has PLA2 and lysophospholipase activities and is the only PLA2 that has specificity for phospholipid substrates containing arachidonic acid. Because of its role in initiating agonist-induced release of arachidonic acid for the production of eicosanoids, cPLA2alpha activation is important in regulating normal and pathological processes in a variety of tissues. Current information available about the biochemical properties and tissue distribution of other Group IV PLA2s suggests they may have distinct mechanisms of regulation and functional roles.