Phosphatidic add

Kishikawa, K., Chahant, C. E, Perry, D. K., Bielawska, A., and Harmrm, Y. A., 1999, Phosphatidic add is a potent and selective inhibitor of protein phosphatase 1 and an inhibitor of cerattride-mediated responses. JBiol Chem 274 21335-21341. 

Fig. 6.11. Formation and function of diacylglycerol. The figure schematically shows two main pathways for formation of diacylglycerol (DAG). DAG can be formed from PtdInsP2 by the action of phospholipase C (PL-C). Another pathway starts from phosphatidyl chohne. Phospholipase D (PL-D) converts phosphatidyl choline to phosphatidic add (Ptd), and the action of phosphatases results in DAG. Arachidonic add, the starting point of biosynthesis of prostaglandins and other intracellular and extracellular messenger substances, can be cleaved from DAG. PKC protein kinase C Ptdins phosphatidyl inositol.

Fig. 2. Targeted lipidomics of 2-AG metabolism. Postulated pathways for 2-AG metabolism. Abbreviations PLC, phospholipase C DAG, diacylglycerol DGL, diacylglycerol lipase MGL, monoacylglycerol lipase PLA, phospholipase A AT, acyltransferase TAGL, triacylglycerol lipase PIP2, phosphatidylinositol bisphosphate ABHD-6/12 hydrolase lyso-PL, lysophospholipid lyso-PA, lysophosphatidic acid PA, phosphatidic add P, phosphatase COX, cydooxygen-ase LOX, lipoxygenase CYP450, cytochrome P450 CDP, cytidine diphosphate.

Phosphoglycerides may be synthesized either from phosphatidic add or by the so-called salvage pathway. Phosphatidic acid is also an intermediate in triglyceride biosynthesis (Figure 19.4). The phosphatidic acid pathway is relatively minor in eukaryotes phosphatidic acid reacts with CTP to form CDP diglyceride (see Figure 19.15), and the latter may then react with choline or inositol to form phosphatidylinositol or phosphatidylcholine, as in Equations (19.14) and (19.15). 

Quinine also has pharmacological activity as an antimalarial, and some studies have been made in order to find a method to diminish or suppress its bitter taste. This can be achieved by adding sweet compounds such as sucrose or aspartame or nonspecific bitter taste inhibitors such as NaCl or phosphatidic add and tannic add [39]. The effects have been studied by sensory evaluation tests in human volunteers, a binding... 

ShddaSD, Hanahan DJ. AGEPC (platelet activating factor) induced stimulation of rabbit platdets Effects on phosphafidylinositol, di- and tri-phosphoinositides and phosphatidic add metdxrlism. Biochem Biophys Res Commm 1982 106 697-703... 

TYSNES OB, Verhoeven AJM, Holmsqi H. Rates of production and consumption of phosphatidic add upon thrombin stimulation of human platel s. EurJ Biochem 174 75-79,1988. 

Lapetina EG, Billah MM, and Cuatrecasas P. (1981). The initial action thrombin on platelets. Conversion of phosphatidylinositol to phosphatidic add pteoeding the production of aradiidcoic add. J. Biol. Chem. 256,5037-5040. 

Fig. 4. Hirombin-mduced loss in pho hatidyIinositol-4,S-bisphosphate (PIPj) and formation of phosphatidic add (PA) was quantified in washed WKY and SHR platelets This Fig. has been adapted from Thromb. Res 49, 5-21,1988.

The inositol phosphates are linked into a metabolic cyde (Fig. 6.6) in which they can be degraded andregenerated. Via these pathways, the cell has the ability to replenish stores of inositol phosphate derivatives, according to demand. Ptdlns may be regenerated from diacylglycerol via the intermediate levels of phosphatidic add and CDP-glycerol. 

Unlike classical neurotransmitters and neuropeptides, AEA and 2-AG are not stored in intracellular compartments but are produced on demand by receptor-stimulated cleavage of lipid precursors. The AEA precursor is an A-arachidonoyl-phosphatidylethanolamine (NArPE), which is cleaved by an as yet imcharacterized A-acylphosphatidylethanolamine (NAPE)-spedlic phospholipase D (E.C. 3.1.4.4 PLD), releasing AEA and phosphatidic add (Di Marzo, 1998 Hansen et al., 2000). A similar route may be operational also for the synthesis of the other cannabimimetic Af-acylethano-lamines, because their precursors, A-acylethanolamine phosphohpids, are ubiquitous constituents of animal and human cells, tissues, and body fluids (Di Marzo, 1998 Hansen et al., 2000). 

Soybean phospholipids (Chapman, 1980) contain phosphatidic add (5%), phosphatidylinositol (20%), phosphatidylethanolamine (23%), phosphatidylcholine (39%) and unidentified components (13%). The phosphatides in crude and degummed soybean oil are given in Table 3.114 (Racicot and Handel, 1983). 

The major pathways for triacylglycerol synthesis are shown in Fig. 11.17. The formation of phos-phatidic acid by the glycerol phosphate pathway or the dihydroxyacetone phosphate pathway has already been discussed (Section 11.2.11). In addition, see reviews by Gurr (1980) and O Doherty (1978). Phosphatidic add can also be formed from... 

For examples of separation of lipids see general references. For tabulated examples, see Ref. B1 for separation of molecular species of phospholipids by HPLC, Ref. I for separation of lipids in food by HPLC, Ref. H for HPLC of phosphatidic add, and Ref. B2 for preparative HPLC of lipids. 

Anionic lipid Alipid displaying at least one net negative charge at physiological pH. Phosphatidic add, phosphati-dylserine, sulfatide, and gangUosides are anionic lipids. 

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