STRUCTURAL AND MECHANISTIC FEATURES OF PHOSPHOLIPASES-C - EFFECTORS OF INOSITOL PHOSPHOLIPID-MEDIATED SIGNAL-TRANSDUCTION

The production of the intracellular second messengers inositol (1,4,5) -trisphosphate (InsP(3)) and sn 1,2-diacylglycerol (DG) in response to a wide variety of extracellular primary messengers is achieved by an extended family of inositol phospholipid phosphodiesterases termed pho spholipases C (PLC, E.C. 3.1.4.11). This family has been the subject o f extensive research and it is clear that the different isoenzymes exh ibit some common characteristics (e.g., interactions with substrates) and other distinctive features (e.g., modes of regulation). The recent description of the X-ray crystal structure of a mammalian PLC has ser ved to clarify much about the behaviour of the PLCs, emphasising the ' 'modular'' structure of these enzymes. The main focus of this review w ill concern the specific adaptations of PLC molecules which make them efficient lipid-metabolising enzymes. We also describe what is known a bout how these enzymes interact with their lipid substrates, which wil l serve as a basis for considering how PLCs may be activated. (C) 1997 Elsevier Science Inc.