Of sphingolipids

FIGURE 25.25 Biosynthesis of sphingolipids in animals begins with the 3-ketosphinga-nine synthase reaction, a PLP-dependent condensation of palmitoyl-CoA and serine. Subsequent rednction of the keto group, acylation, and desatnration (via rednction of an electron acceptor, X) form ceramide, the precnrsor of other sphingolipids. 

In multiple sclerosis, which is a demyelinating disease, there is loss of both phospholipids (particularly ethanolamine plasmalogen) and of sphingolipids from white matter. Thus, the lipid composition of white matter resembles that of gray matter. The cerebrospinal fluid shows raised phospholipid levels. 

The use of sphingolipids in liposome formation is possible due to the natural amphipathic properties of the molecules. Some sphingolipids can lend structural advantages to the integrity... 

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.

Methods of assessing transmembrane movement of sphingolipids have been reviewed by Sillence et al. (2000). 

Figure 1. Scheme of sphingolipid metabolism and the central role of ceramide and ceramidases. 

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). 

Gatt, S., 1963, Enzymatic hydrolysis of sphingolipids. 1. Hydrolysis and synthesis of ceramides by an enzyme from rat brain. J. Biol. Chem. 238 3131-3133. 

Lehtonen, J.Y.A., Horiuchi, M., Daviet, L., AMshita, M. and Dzau, V.J., 1999, Activation of the de novo biosynthesis of sphingolipids mediates angiotensin 11 type 2 receptor-induced apoptosis. J. Biol. Chem. 274 16901-16906. 

Markey SP, Wenger, DA. 1974. Mass spectra of complex molecules. I. Chemical ionization of sphingolipids. Chem Phys Lipids 12 182. 

Harder T, Simons K. Caveolae, DIGs, and the dynamics of sphingolipid-cholesterol microdomains. Curr Opin Cell Biol 1997 9 534-542. 

Wang, E. et ah, Inhibition of sphingolipids biosynthesis by fumonisin, implication for diseases associated with Fusariurn moniliforme, J. Biol. Chem., 266, 14486, 1991. 

Sonicate the test tubes in a bath-type sonicator until they appear evenly dispersed incubate overnight at 48°C in a heating block. This heating step can often be shortened, but it is conventional in the extraction of sphingolipids because they have high phase transition temperatures. 

Bartke, N., Fischbeck, A., Humpf, H. U. (2006). Analysis of sphingolipids in potatoes Solanum tuberosum L.) and sweet potatoes Ipomoea batatas (L.) Lam.) by reversed phase high-performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESl-MS/MS). Mol. Nutr. Food Res., 50,1201-1211. 

B. Kaufman, 8. Basu, and S. Roseman, in 8. M. Aronson and B. N. Volk (Eds.), Inborn Disorders of Sphingolipid Metabolism, Proc.. Int. Symp. Cerebral Sphin-golipidoses, 3rd, Pergamon Press, Oxford and New York, 1966, pp. 193-213. 

Kolter T, Sandhoff (2005) Principles of lysosomal membrane digestion stimulation of sphingolipid degradation by sphingolipid activator proteins and anionic lysosomal lipids. Annu Rev Cell Dev Biol 21 81-103... 

Vitamin B6 occurs naturally in three related forms pyridoxine (6.26 the alcohol form), pyridoxal (6.27 aldehyde) and pyridoxamine (6.28 amine). All are structurally related to pyridine. The active co-enzyme form of this vitamin is pyridoxal phosphate (PLP 6.29), which is a co-factor for transaminases which catalyse the transfer of amino groups (6.29). PLP is also important for amino acid decarboxylases and functions in the metabolism of glycogen and the synthesis of sphingolipids in the nervous system. In addition, PLP is involved in the formation of niacin from tryptophan (section 6.3.3) and in the initial synthesis of haem. 

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