Diglycerides diacylglycerols

Draw the general structural formula of each of the following classes of compound (a) a (3-amino acid, (b) a nucleotide, (c) a plasmalogen, (d) an a-amino acid, (e) a tripeptide and (f) a diacylglycerol (diglyceride). 

Fats and oils contain various classes of compounds (16). These componds are primarily neutral lipids that include triacylglycerols (triglycerides) with lower amounts of diacylglycerols (diglycerides), monoacylglycerols (monoglycerides),... 

B. Monoacylglycerols (monoglycerides), diacylglycerols (diglycerides), and triacylglycerols (triglycerides) contain one, two, and three fatty acids esterified to glycerol, respectively. 

Diacylglycerols (diglycerides) Two moles of fatty acid/mole of glycerol Trace levels in animal and plant tissues... 

This enzyme [EC 2.3.1.20], also known as diglyceride acyltransferase, catalyzes the reaction of an acyl-CoA with 1,2-diacylglycerol to produce coenzyme A and a triacylglycerol. The acyl-CoA derivative can be palmi-toyl-CoA or other long-chain acyl-CoA compounds. 

This enzyme [EC 3.1.1.34] (also called clearing factor lipase, diglyceride lipase, and diacylglycerol lipase) catalyzes the hydrolysis of a triacylglycerol to produce a diacylglycerol and a fatty acid anion. This enzyme hydrolyzes triacylglycerols in chylomicrons and in low-density lipoproteins and also acts on diacylglycerols. See also Lipases... 

Chau L. Y. and Tai H. H. (1981). Release of arachidonate from diglyceride in human platelet requires the sequential action of a diacylglycerol lipase and a monoglyceride lipase. Biochem. Biophys. Res. Commun. 100 1688-1695. 

Heinze, F. J., Linscheid, M., and Heinz, E. (1984) Release of diacylglycerol moieties from various glycosyl diglycerides, Anal. Biochem. 139, 126-133. 

The pathways diverge at phosphatidate. In the synthesis of triacylglycerols, phosphatidate is hydrolyzed by a specific phosphatase to give a diacylglycerol (DAG). This intermediate is acylated to a triacylglycerol in a reaction that is catalyzed by diglyceride acyltransferase. Both enzymes are associated in a triacylglycerol synthetase complex that is bound to the endoplasmic reticulum membrane. 

In this process, an oil (triacylglycerol, also known as triglyceride) molecule reacts with a molecule of water, releasing a molecule of fatty acid (12), commonly known as free fatty acid (FFA), and a molecule of diacylglycerol (DG, also called diglyceride). The reaction scheme is shown below ... 

The 2,4-dinitrobenzyl diglyceride (85) has been synthesized as a means of photoactivating protein kinase C (PKC). PKC is inactive in the cytoplasm until its primary activator, a diacylglycerol, is produced by phospholipase C. Upon photolysis (85) releases dioctanoylglycerol, and thus provides an approach to the controlled activation of PKC. 

Phosphatidic acid lies at a metabolic branch point. On the one hand, the phospho group can be removed by a specific phosphatase (step d) and another acyl group (most often an unsaturated acyl group) may be transferred onto the resulting diacylglycerol (DAG, diglyceride, step to form a triacylglycerol... 

Diacylglycerols behave similarly. The equilibrium mixture of 1,2- (40%) and 1,3- (60%) isomers varies somewhat with temperature. Saturated diglycerides isomerize in the solid state to virtually 100% of the 1,3-isomer. 

Based on this fact and in the presence of active phosphoinositide phosphodiesterases, these authors proposed a relationship between arachidonoyl diglycerides and the phosphoinositides in the central nervous system. The rapid production of diacylglycerols enriched in 18 0-20 4 that takes place in the mammalian brain during ischemia (Aveldano Bazan, 1975), may be related to this possibility. By analogy we suggested that such a metabolic link might also be present in the mammalian retina (Aveldano Bazan, 1974). 

---