Sphingolipids acids

We turn now to the biosynthesis of lipid structures. We begin with a discussion of the biosynthesis of fatty acids, stressing the basic pathways, additional means of elongation, mechanisms for the introduction of double bonds, and regulation of fatty acid synthesis. Sections then follow on the biosynthesis of glyc-erophospholipids, sphingolipids, eicosanoids, and cholesterol. The transport of lipids through the body in lipoprotein complexes is described, and the chapter closes with discussions of the biosynthesis of bile salts and steroid hormones. 

Fig. 14.—Schematic Representation of the Fragmentation Observed in the Positive F.a.b.-Mass Spectrum of a Permethylated Ganglioside Isolated from Granulocytes. [Other glyco-sphingolipids fragment in a similar way. Major cleavages are shown with solid lines, and minor cleavages with dotted lines. The masses of ions resulting from cleavages (a), (b), and (c) define the type of sphingosine and the type of fatty acid. In this example, (a) is 548, (b) is [M + H] minus 238, and (c) is [M + H] minus 533.]...

Marine sponges have long been recognized as a source of novel lipids including unique branched and elongated fatty acids, often found incorporated into phospholipids, triglycerides, and sphingolipids [20-23]. 

Figure 22.6 Sphingolipids are constructed of sphingosine derivatives containing an acylated fatty acid and a head group attached to the hydroxyl.

Glycerolipids are derivatives of glycerol and fatty acids 34 In sphingolipids, the long-chain aminodiol sphingosine serves as the lipid backbone 37... 

Acetyl coenzyme A is the precursor of both cholesterol and fatty acids 39 Phosphatidic acid is the precursor of all glycerolipids 42 Sphingolipids are biosynthesized by adding head groups to the ceramide moiety 44... 

FIGURE 3-3 Structure of some simple sphingolipids. X may be a complex polysaccharide either containing sialic acid (gangliosides) or not (globosides). See also Figures 3-4 and 3-9 for the nomenclature and structure of some of the complex brain sphingolipids. 

Figure 12.12 Sphingomyelins. Sphingomyelins are esters of a ceramide and phospho-ryl choline. However, similar compounds are ceramide-1-phosphoryl ethanolamines and phosphono forms of sphingolipids. Ceramides W-acyl-sphingosines) are amides of a long chain di- or trihydroxy base containing 12 to 22 carbon atoms, of which sphingosine (4-sphingenine) is the commonest, and a long chain fatty acid whose acyl chain is shown by R1. This may contain up to 26 carbon atoms.

Acid CDase is localized in the lysosomes and it is suggested that it plays an important role in the catabolic pathway of sphingolipids. It has been also suggested recently, to play a role in apoptosis in response to TNFa induced death ofL929 cells (Strelow etal, 2000). 

Linke, T., Wilkening, G., Sadeghlar,. F, MozcaU, H., Bernardo, K., Schuchman, E., and Sandhoff, K., 2001, Interfacial Regulation of Acid Ceramidase Activity. Stimulation of ceramide degradation by lysosomal lipids and Sphingolipid Activator Proteins. J. Biol. Chem. 276 5760-5768. 

Serine (Ser or S) ((S)-2-amino-3-hydroxypropanoic acid) is a polar, neutral, uncharged amino acid with the formula H00CCH(NH2)CH20H. It has an aliphatic hydroxyl side chain and can be seen as a hydroxylated version of Ala. Ser participates in the biosynthesis of purines and pyrimidines and is also the precursor to several amino acids including Gly, Cys, and Trp (in bacteria). In addition, it is the precursor to numerous other metabolites, including sphingolipids and is present in enzymes such as a-chymotrypsin. Ser, Asn, and aspartate disrupt a helices. 

Acidic Phospholipids Phospholipids Phosphoinositides Phosphoinositides Neutral Lipids like MAG, DAG and TAG Sphingolipids... 

The pathways for the synthesis of phosphoglycerides and sphingolipids are described in detail in Chapter 11. They are, therefore, described only in brief here in order to emphasise the importance of the essential fatty acids in proliferation and how the cell cycle could be impaired by failure to provide these acids. 

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