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phospholipase

(Science: enzyme) That hydrolyse ester bonds in phospholipids. They comprise two types: aliphatic esterases (phospholipase A1, A2 and B) that release fatty acids and phosphodiesterases (types C and D) that release diacyl glycerol or phosphatidic acid respectively.

type A2 is widely distributed in venoms and digestive secretions. Types A1, A2 and C the latter specific for phosphatidyl inositol) are present in all mammalian tissues. Type C is also found as a highly toxic secretion product of pathogenic bacteria. Type B attacks monoacyl phospholipids and is poorly characterised. Type D is largely of plant origin. PLA2 Type II (a secreted enzyme, but not the same as the Type I digestive pancreatic enzyme) is probably very important in inflammation because its action can release arachidonic acid, the starting point for eicosanoid synthesis.

phosphatidyl inositol bisphosphate specific phospholipase C is important in generating diacyl glycerol and inositol trisphosphate, both second messengers.