Glycerol diacyl

Eicosanoids, so named because they are all derived from 20-carbon fatty acids, are ubiquitous breakdown products of phospholipids. In response to appropriate stimuli, cells activate the breakdown of selected phospholipids (Figure 25.27). Phospholipase Ag (Chapter 8) selectively cleaves fatty acids from the C-2 position of phospholipids. Often these are unsaturated fatty acids, among which is arachidonic acid. Arachidonic acid may also be released from phospholipids by the combined actions of phospholipase C (which yields diacyl-glycerols) and diacylglycerol lipase (which releases fatty acids). 

There are several subfamilies of PKs, which either require Ca2+, diacyl glycerol or phorbol esters or extracellular agonists for activation. Four major groups of PKs are distinguished. Basic amino acid-directed kinases (PKA, PKB, PKC) phophorylate serine/threonine around such amino acid residues. PKA is activat-... 

Transfer of an additional acyl residue to DAG forms triacylglycerols (enzyme diacyl-glycerol acyltransferase 2.3.1.20). This completes the biosynthesis of neutral fats. They are packaged into VLDLs by the liver and released into the blood. Finally, they are stored by adipocytes in the form of insoluble fat droplets. 

This enzyme [EC 2.7.8.11], also known as CDP-diacyl-glycerol—inositol 3-phosphatidyltransferase, catalyzes the reaction of CDP-diacylglycerol with myo-inositol to produce CMP and phosphatidyl-lD-myo-inositol. 

Its mechanism of action is not well understood. Some possible actions include inhibition of norepinephrine release and increased re-uptake of norepinephrine and serotonin. It also possibly increases the synthesis and turnover of serotonin. Lithium interferes with the production and release of the second messengers phosphatdylinositol-4,5-bisphosphate and diacyl glycerol. Finally it may uncouple receptor recognition sites from GTP-binding protein by competing with Mg++. 

Cyclic carbohydrates with two alkyl chains (e.g. 1,2-dialkyl (or 1,2-diacyl) glycerol 8 a (sug=Glcp, Galp) present structural similarities with glycerophospho-lipids. They form complex mesophases such as bicontinuous cubic phases, inverted hexagonal phases or myelin figures [58-61]. Other dialkyl derivatives... 

Sodium bis(2-ethyl-l-hexyl) sulfosuccinate (Aerosol OT, AOT) sodium do-decylbenzene sulfonate (SDBS) sodium di-2-ethyl hexyl phosphate (NaDEHP) dioleyl phosphoric acid (DOLPA) di(tridecyl) phosphoric acid (DTDPA) sodium dodecyl sulfate (SDS) 1,3-dilauroyl glycerol-2-disodium phosphate (2-modified 1,3-diacyl glycerol)... 

Adrenergic receptors These are membrane bound G-protein coupled receptors which function primarily by increasing or decreasing the intracellular production of second messengers cAMP or inositol triphosphate (IP3)/diacyl glycerol (DAG). Adrenergic receptors are classified into two main groups [Pg.131]

Cleavage of inositol-containing phospholipids by phospholipase C is of particular regulatory importance. Phospholipase C catalyzes the release of diacyl glycerol and inositol-l,4,5-triphosphate from phosphatidyl inositol-4,5-diphosphate, a phospholipid... 

Messenger substances with hydrophobic character such as diacyl glycerol or the phosphatidyl inositol derivatives are membrane localized. The hydrophobic messengers reach membrane-associated effector proteins by diffusing through the plasma membrane and there regulate their activity. 

Two functions are attributed to the binding of the activating cofactors Ca, diacyl-glycerol and phospholipid ... 

Furthermore, the LPS signal transduction involves the activation of G proteins, of phospholipases C and D, the formation of diacyl-glycerol (DG) and inositol triphosphate (IP3). DG mediates the stimulation of protein kinase C (PKC) and IP3 induces an increase of cytosolic Ca++ The LPS signaling pathway also involves tyrosine kinases, constitutive nitric oxide (NO) synthase (cNOS), cGMP-dependent protein kinase, Ca channels, calmodulin and calmodulin kinase [27,28], as well as the MAP kinases [29] ERK1, ERK2 and p38 [23], The intracellular events in response to LPS are due to lipid A because they are inhibited by polymyxin B which is known to bind lipid A [27] and they are reproduced by lipids A [30,31]. 

A second class of serpentine receptors are coupled through a G protein to a plasma membrane phospholipase C (PLC) that is specific for the plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (see Fig. 10-15). This hormone-sensitive enzyme catalyzes the formation of two potent second messengers diacyl-glycerol and inositol 1,4,5-trisphosphate, or IP i (not to be confused with PIP3, p. 431). 

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. 

Phospholipids General structure of a phospholipid PHOSPHOLIPIDS (p. 199) Phospholipids are polar, ionic compounds composed of an alcohol (for example, choline, ethanolamine, serine, and glycerol) attached by a phosphodiester bridge to either diacyl-glycerol or to sphingosine. 

Marshall, M. O. and Knudsen, J. 1980. Factors influencing the in vitro activity of diacyl-glycerol acyltransferase from bovine mammary gland and liver towards butyryl-CoA and palmitoyl-CoA. Biochim. Biophys. Acta 617, 393-397. 

The three-dimensional structure of cholera toxin.6 Side view of the p subunit pentamer as a ribbon drawing. Bound noncovalently to it are five molecules of the ganglioside Gm1 (compare with the structure in Fig. 7-5). The diacyl glycerol parts of the gangliosides are buried in the membrane that lies below the toxin molecule. Courtesy ofW.G.J. Hoi. 

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