Glycerophospholipids phosphatidic acid

Glycerophospholipids. Phosphatidic acids, for example (1), can be esterified directly by use of TPS in the presence of pyridine to give glycerophospholipids (2).1... 

LPA can be produced by several enzymatic routes (Figure 4). However, the relative contributions of these to LPA production is not known since specific inhibitors for many of the enzymes involved are not available (Pages et al., 2001). Firstly, de novo biosynthesis of LPA occurs by acylation of glycerol 3-phosphate, catalysed by glycerophosphate acyltransferase, in both the endoplasmic reticulum and mitochondria. Alternatively, LPA can be synthesized by the phosphorylation of monoacylglycerol or, in peroxisomes, by the reduction of acyl dihydroxyacetone phosphate. Subsequently, acylation of LPA by monoacylglycerolphosphate acyltransferase produces the precursor of all glycerophospholipids, phosphatidic acid. The latter can also act as a precursor of LPA synthesis by phospholipase A-catalysed deacylation. 

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... 

The simplest of the glycerophospholipids is phosphatidic acid, in which phosphate is linked to the third hydroxyl function, forming a phosphate ester. More complex glycerophospholipids are derivatives of phosphatidic acid in which one of several groups is attached commonly choline, ethanolamine, serine, or myo-inositol. Structures are collected in table 19.1. 

Phosphatidic acid the structural backbone of the glycerophospholipids two molecules of fatty acids are esterified to a molecule of glyceryl phosphate. 

Figure 4-1. Structures of the membrane bilayer and an amphipathic phospholipid. The head group attachment, X, may be H as in phosphatidic acid or one of several substituents linked via phosphoesters in the glycerophospholipids. The nonpolar tail is depicted as composed of saturated fatty acids in this molecule. The overall length of the hydrocarbon chain of the fatty acids may vary from 14 to 20.

FIGURE 10-8 Glycerophospholipids. The common glycerophospho-lipids are diacylglycerols linked to head-group alcohols through a phosphodiester bond. Phosphatidic acid, a phosphomonoester, is the... 

FIGURE 21-18 Phosphatidic acid in lipid biosynthesis. Phosphatidic acid is the precursor of both triacylglycerols and glycerophospholipids. The mechanisms for head-group attachment in phospholipid synthesis are described later in this section. 

The first steps of glycerophospholipid synthesis are shared with the pathway to triacylglycerols (Fig. 21-17) two fatty acyl groups are esterified to C-l and C-2 of L-glycerol 3-phosphate to form phosphatidic acid. Commonly but not invariably, the fatty acid at C-l is saturated and that at C-2 is unsaturated. A second route to phosphatidic acid is the phosphorylation of a diacyl-glycerol by a specific kinase. 

A. Structures of some glycerophospholipids. B. Phosphatidic acid. = phosphate, PO4-2. 

Glycerophospholipids are formed from phosphatidic acid and an alcohol The phosphate group on phosphatidic acid (PA) can be esterified to another compound containing an alcohol group (aee... 

Definition and example of a glycerophospho-lipid Phospholipids that contain glycerol are called glycerophospholipids or phosphoglyc-erides. All contain phosphatidic acid, the simplest glycerophospholipid. When an alcohol, such as choline, is esterified to phosphatidic acid, the product is phosphatidylcholine. 

Structure and function of cardiolipin Cardiolipin contains two molecules of phosphatidic acid esterified through their phosphate groups to an additional molecule of glycerol. This is the only human glycerophospholipid that is antigenic. It is an important component of the inner mitochondrial membrane. 

Glycerophospholipids contain a glycerol skeleton to which two fatty acids are esterified saturated fatty acids occupy mostly sn-position 1, whereas unsaturated fatty acids are mainly present on sn-position 2. The third hydroxyl is linked to a phosphate group to which an organic base is mostly esterified (Fig. 1). The most important components of soybean lecithin are phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinositol (PI). Phosphatidic acid (PA) may become important due to the presence of phospholipase D this enzyme slowly converts PC into PA in vegetable lecithins. Phosphatidylserine (PS), phosphatidylglycerol (PG), and lyso-phosphatidylcholine (LPC) are known as minor components lysophospholipids contain only one acyl group per molecule. Besides, ether phospholipids occur in which one or both fatty acyl... 

Examples include lecithin, cephalin, sphingomyelin, phosphatidic acid, and plasmalogen. Two types of phospholipids exist glycerophospholipid and sphingosyl phosphatide. A synthetic phospholipid, alkylphosphocholine, has been used in biological and therapeutic areas. 

An intermediate in glycolysis, gluconeogenesis, glycerophospholipid, glycerol metabolism, phosphatidic acid synthesis, fat metabolism, and the Calvin Cycle. 

Phosphatidic Acid (also know as diacylglycerol-3-phosphate) is formed by esterification of glycerol-3-phosphate with two fatty acids. Phosphatidic acid is an important intermediate in synthesis of fats and glycerophospholipids. In fat synthesis, the phosphate from phosphatidic acid is removed to form 1,2-diacylglycerol and then a third fatty acid is esterified to yield 2... 

Phosphatidic acid is a branch point between the synthesis of fats and other glycerophospholipids. The high energy anhydride bond between the cytidylic and phosphatidic acid in CDP-diacylglycerol provides an activated intermediate for addition of polar head groups on the phosphate. 

Figure 19.2 schematically depicts the primary pathways of prokaryotic and eukaryotic glycerophospholipid biosynthesis. Note that the center pathway shown in purple occurs in both prokaryotic and eukaryotic cells. Phosphatidic acid, the branch point between the synthesis of fats and other glycerophospholipids, can be made via three different pathways in eukaryotes-from glycerol-3-phosphate (Figure 19.3), from diacylglycerol (Figure 19.2), and from dihydroxyacetone phosphate (DHAP) (see here). 

Phosphatidylinositol is uncommon in bacteria and is found in a few Gram-positive species only. In actinomycetes and a few other bacteria mannosides of phosphatidylinositol may be present. Other glycerophospholipids such as phosphatidic acid and phosphatidylserine have a widespread occurrence in bacteria but only in small amounts. Both of these lipids play an important role as metabolic intermediates (Finnerty, 1978 Raetz, 1978). 

The breakdown of glycerophospholipids is catalysed by a series of phospholipases designated A, B, C and D depending on their positions of attack (Fig. 11.16). In addition, phosphatidic acid phosphatase is important, but this has already been dealt with (Section 11.2.1). Two phospholipase A specificities are recognized and these are named Ai and A2 depending on the position of the ester hydrolysed in the diacylphosphoglyceride. Phospholipase B is the name usually used for an enzyme which is a... 

Fig. 3. Membrane lipids. Basic structures of phosphatidyl- and plasmenyl glycerophospholipids along with those of phosphatidic acid and plasmenic acid.

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