Acids phosphatidic

The parent compound of the glycerophosphatides is L-a-phosphatidic acid (I), a substance now known to be an important intermediate in the biosynthesis of most of these lipids. 

When cell-free tissue preparations are incubated in the presence of inorganic 2, much of the radioactivity may be recovered from phosphatidic acid, whereas 

Kornberg and Pricer (1953 a) showed that guinea pig liver contains an acyl CoA synthetase system (Acid CoAligase (AMP) EC 6.2.1.3) capable of catalysing the activation of long-chain fatty acids with the formation of thioesters of CoA according to the overall equation  

Subsequently, a similar reaction was observed in brain (Vignais, Gallagher and Zabin 1958) and other tissues (Senior and Isselbacher 1960). 

Vignais and Zabin (1958) provided evidence that the reaction, like the activation of acetate, occurs in the following two steps  

A set of ions at m/z 227,209, 171, and 153 in low abundance corresponding to the combined loss of a FA ketene and a fatty acid, the loss of fatty acids, glycerol phosphate, and a phosphoglycerol derivative, respectively, are the indicative of 

There exist some occasions that PG fragmentation does not follow the pattern discussed earlier. For example, PG species from Arabidopsis thaliana contain an unusual FA chain, 3-trans-hexadecenoyl, at the sn-2 position [48]. Product-ion ESI-MS spectra of deprotonated PG species after CID all demonstrate a predominant [M-H-236] ion, resulting from the loss of the 3-rrans-hexadecenoyl moiety as a ketene. 

Fragmentation of protonated PA species after CID demonstrates a predominant fragment ion corresponding to the loss of phosphoric acid (i.e., [M- -H-(H0)2P(0)0H] ) [1]. This ion is consistent with the notion that the gas-phase phosphoric acid is less competitive for a proton to form the protonated (H0)2P(0)0H. The acylium ions as well as the ions arising from further dissociation of [M- -H-H0)2P(0)0H]+ via the loss of the FA substituents as ketenes at positions sn-l and sn-2, respectively, are present in the spectra in low abundance. Although the FA identities can be determined from these ions with efforts, assigning the regiospecific positions of 

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Triacylglycerols arise not by acylation of glycerol itself but by a sequence of steps m which the first stage is acyl transfer to l glycerol 3 phosphate (from reduction of dihy droxyacetone 3 phosphate formed as described m Section 25 21) The product of this stage IS called a phosphatidic acid... 

Hydrolysis of the phosphate ester function of the phosphatidic acid gives a diacylglycerol which then reacts with a third acyl coenzyme A molecule to produce a triacylglycerol... 

Fig. 1. Chemical stmcture of phosphatidylcholine (PC) (1) and other related phosphohpids. R C O represents fatty acid residues. The choline fragment may be replaced by other moieties such as ethanolamine (2) to give phosphatidylethanolamine (PE), inositol (3) to give phosphatidylinositol (PI), serine (4), or glycerol (5). IfH replaces choline, the compound is phosphatidic acid (6). The corresponding lUPAC-lUB names ate (1), l,2-diacyl-t -glyceto(3)phosphocholine (2), l,2-diacyl-t -glyceto(3)phosphoethanolamine (3), 1,2-diacyl-t -glyceto(3)phosphoinositol (4), 1,2-diacyl-t -glyceto(3)phospho-L-serine and (5), l,2-diacyl-t -glyceto(3)phospho(3)-t -glycetol.

In addition to the triglycerides, the four oilseeds also contain phosphatides. For example, soybean oil containing 1.47% phosphatides consists of 48.9% phosphatidylcholine, 27.0% phosphatidylethanolamine, 21.9% phosphatidjlinositol and 2.2% phosphatidic acid (24). Total phosphatides of cottonseed and peanut kernels are estimated to be 1.5—1.9 and 0.8%, respectively (25). 

Phosphatidic acids not only are intennediates in the biosynthesis of triacylglycerols but also are biosynthetic precursors of other members of a group of compounds called phosphoglycerides or glycerol phosphatides. Phosphorus-containing derivatives of lipids are known as phospholipids, and phosphoglycerides are one type of phospholipid. 

FIGURE 8.4 Phosphatidic acid, the parent compound for glycerophospholipids. 

Phosphatidic acid, the parent compound for the glycerol-based phospholipids (Figure 8.4), consists of 5w-glycerol-3-phosphate, with fatty acids esterified at the T and 2-positions. Phosphatidic acid is found in small amounts in most natural systems and is an important intermediate in the biosynthesis of the more common glycerophospholipids (Figure 8.6). In these compounds, a... 

FIGURE 25.18 Synthesis of glycerolipids in eukaryotes begins with the formation of phosphatidic acid, which may be formed from dihydroxyace-tone phosphate or glycerol as shown. 

Phosphatidic acid Phosphatidylcholine Phosphatidyl- ethanolamine Phosphatidylserine... 

Lipid phosphate phosphohydrolases (LPPs), formerly called type 2 phosphatidate phosphohydrolases (PAP-2), catalyse the dephosphorylation of bioactive phospholipids (phosphatidic acid, ceramide-1-phosphate) and lysophospholipids (lysophosphatidic acid, sphingosine-1-phosphate). The substrate selectivity of individual LPPs is broad in contrast to the related sphingosine-1-phosphate phosphatase. LPPs are characterized by a lack of requirement for Mg2+ and insensitivity to N-ethylmaleimide. Three subtypes (LPP-1, LPP-2, LPP-3) have been identified in mammals. These enzymes have six putative transmembrane domains and three highly conserved domains that are characteristic of a phosphatase superfamily. Whether LPPs cleave extracellular mediators or rather have an influence on intracellular lipid phosphate concentrations is still a matter of debate. 

Phosphatidic acid is glycerol esterified at the sn-1 and sn-2 positions to two fatty acids and at the sn-3 position to phosphoric acid. It is a product of phospholipase D action that is also an intermediate in the biosynthesis of phosphatidylseiine and phosphatidylinositol. 

Gainesis N., and Hauser, H. (1983). Characterization of small unilamellar vesicles produced in unsonicated phosphatidic acid and phosphatidylcholine-phosphatidic acid dispersions by pH adjustment, Biochim. Biophys. Acta, 731. 31-39. 

The SUM was covered by a polymer film with an orifice of approximately 0.3 mm in diameter on each side, and subsequently a folded BLM was generated from a DPhPC/l,2-dipalmitoyl-in-glycero-3-phosphatidic acid (DPPA) monolayer on the side facing the SUM (Fig. 19). Interestingly, no pretreating of the orifice with any alkane or lipid was required, as is imperative for all other BLM techniques. Thus, an accumulation of such compounds could be excluded, and the physicochemical properties of the membrane and... 

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