Receptors for a growing family of secreted phospholipases A(2)

Phospholipases A(2) (PLA(2)s) are enzymes that catalyse the hydrolysis of t he sn-2 acyl bond of glycerophospholipids to produce free fatty acids and l ysophospholipids. Numerous intra cellular and secreted PLA(2)s (sPLA(2)s) h ave now been characterized. Because PLA(2) products are important for cell signalling and the biosynthesis of biologically active lipids, including ei cosanoids and platelet-activating factor, PLA(2)s are generally considered as key enzymes that control the release of lipid mediator precursors. Howev er, the increasing number of mammalian sPLA(2)s and the recent identificati on of different membrane proteins that bind sPLA(2)s makes it likely that t hese enzymes also behave as ligands for receptors, and that their physiolog ical function is not limited to their catalytic activity. Here, the current state of awareness regarding the different types of sPLA(2)-binding protei ns is described. To date, five distinct mammalian sPLA(2)s and two main typ es (M and N) of sPLA(2) receptors have been identified. Because most is kno wn about the M-type receptor, particular attention will be paid to it, incl uding a description of it molecular properties and of its possible biologic al roles with regard to sPLA(2) function.