Phospholipase A1: structure, distribution and function

AbstractPhospholipase (PL)A1 is an enzyme that hydrolyzes phospholipids and produces 2-acyl-lysophospholipids and fatty acids. Although PLA1 activities have been detected in many organisms and tissues, their functions have not been elucidated until recently. Currently, six extracellular and three intracellular PLA1 enzymes are known in mammals. The extracellular PLA1s consist of phosphatidylserine (PS)-specific PLA1 (PS-PLA1), membraneassociated phosphatidic acid (PA)-selective PLA1s (mPA-PLA1 and mPA-PLA1 ), hepatic lipase (HL), endothelial lipase (EL) and pancreatic lipas–elated protein (PLRP)-2, all of which belong to the lipase gene family. PS-PLA1, EL, mPA-PLA1 and mPA-PLA1 prefer phospholipid substrates, whereas HL and PLRP-2 show both PLA1 activity and lipase activity to hydrolyze triacylglycerol. EL has a role in high-density lipoprotein (HDL) metabolism by hydrolyzing phosphatidylcholine on HDL particles. PS-PLA1, mPA-PLA1 and mPA-PLA1 have distinct structural features in two surface loops (the lid and the 9 loop), which are implicated in substrate recognition. PS-PLA1, mPA-PLA1 and mPA-PLA1 specifically hydrolyze PS and PA, respectively, and produce their corresponding lysophospholipids (lysophosphatidylserine and lysophosphatidic acid), which have been defined as lipid mediators with multiple biological functions. Thus, these PLA1s may have a physiological role in the production of these lysophospholipid mediators. The intracellular PLA1s consist of PA-preferring PLA1, KIAA0725p and p125 in mammals, all of which are conserved in a wide range of organisms and have been implicated in vesicular transport.Keywords: lipaselysophosphatidic acidlysophosphatidylserinephosphatidic acidphosphatidylserinephospholipase A1