Cellular phospholipases

Cabot MC, Zhang Z, Cao H, Lavie Y, Giuliano AE, Han TY, Jones RC (1997) Tamoxifen activates cellular phospholipase C and D and elicits protein kinase C translocation. Int J Cancer 70(5) 567-574... 

Shoshan MC, Florin I, Thelestam M (1993a) Activation of cellular phospholipase A2 by Clostridium difficile toxin B. In J. Cell. Biochem. 52 116-124. 

P. Pernas, J.L. Olivier, M.D. Legoy, and G. Bereziat Phospholipid synthesis by extra cellular phospholipase Aj in organic solvents. Biochemical and Biophysical Research Communications 168 (1990) 655-650. 

As expected, earlier studies focused on mechanisms that involve eicosanoid metabolites. More recently, however, the effects of fatty acids on gene expression have been investigated and this focus of interest has led to studies at the molecular level (Tables 8, 9). Previous studies have shown that fatty acids, whether released from membrane phospholipids by cellular phospholipases or made available to the cell from the diet or other aspects of the extracellular environment, are important cell signaling molecules. They can act as second messengers or substitute for the classic second messengers of the inositide phospholipid and cyclic AMP signal transduction pathways. They can also act as modulator molecules mediating responses of the cell to... 

Interest in the PGs has recently reverted to their precursor arachidonic acid (AA), which seems to be able to act intracellulary as a second messenger, and also extra-cellularly. In this latter mode it may play a part in LTP. It is known that AA produces a long-lasting enhancement of synaptic transmission in the hippocampus that resembles LTP and in fact activation of NMDA receptors leads to the release of AA by phospholipase A2 (see Dumuis et al. 1988) and inhibition of this enzyme prevents the induction of LTP. AA has also been shown to block the uptake of glutamate (see Williams and Bliss 1989) which would potentiate its effects on NMDA receptors. This would not only prolong LTP but also cause neurotoxicity. 

Cellular lipoxygenases have been implicated as possible enzymatic mediators of endothelial cell-dependent oxidation of LDL. Inhibitors of lipoxygenase, but not cyclooxygenase, have been shown to be effective inhibitors of LDL oxidation using rabbit endothelial cells (Parthasarathy etal., 1989). Interestingly, a phospholipase A2 activity intrinsic to apo-B has also been implicated in the endothelial cell-dependent modification of LDL (Parthasarathay et al., 1985). 

Figure 4 Schematic representation of the Ca2+-transporting systems affecting cellular calcium homeostasis during hormonal stimulation, oq = oq-adrenergic receptor VP = vasopressin receptor PLC = phospholipase C PI = phosphatidylinositol PIP = phospha-tidylinositol-4-phosphate PIP2 = phosphatidylinositol-4,5-biphosphate IP3 = inositol-1,4,5-triphosphate DG = diacylglycerol PKC = protein kinase C. (Modified from Refs. 125 and 285.)...

Phorbol esters are promoters that interact with cellular receptors and activate protein kinase C. Usually protein kinase C is activated by Ca++ and diacylglycerol, both of which result from the hydrolysis of phosphoinositides catalyzed by phospholipase C. Phospholipase C is normally activated by several different growth factors. Thus phorbol esters bypass a tightly regulated step in the control of cell growth. Since protein kinase C phosphorylates various proteins, it is not known how this activity participates in establishing a cancerous line of cells. 

ZENECA has developed a non-solvent based recovery process as an alternative to solvent extraction for the commercial production of poly(3HB) and poly(3HB-co-3V) by A. eutrophus [94,95], In this process the cells were first exposed to a temperature of 80 °C and subsequently treated with a cocktail of various hydrolytic enzymes consisting of lysozyme, phospholipase, lecithinase, the proteinase alcalase, and others. Most of the cellular components were hy-... 

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