Sphingomyelin fatty acids

Extensive studies of the sphingomyelin fatty acids of brain lipids by Stallberg-Stenhagen and Svennerholm (1965) have shown that there is a common abnormality in all infantile cases of hereditary disorders of lipid metabolism in that... 

Early data on the composition of brain sphingomyelin fatty acids in NPD are contradictory Klenk (1934) reported a normal sphingomyelin fatty acid pattern, stearic acid being the most prominent component Thannhauser (1957) found only traces of nervonic acid which normally makes up 12—15% of brain sphingomyelin fatty acids. 

Values expressed as per cent of total brain sphingomyelin fatty acids.) From Stallberg-Stenhagen and Svennerholm (1965). 

The sphingomyelin fatty acid pattern as reported for NPD is strikingly similar to that of fetal brain and thus resembles findings in other lipidoses with central nervous system involvement. 

SwEELEY (1960,1963) examined plasma sphingomyelin fatty acids in NPD and found 18 different fatty acids with chain lengths from C-12 to C-24. As in normals, palmitic acid was the main component. 

Dihydrosphingosine and homologues with longer chain lengths are apparently present in small amounts in NPD, as is the case in normals. Whether persistence of a fetal sphingomyelin fatty acid pattern may be the cause or the result of storage, remains to be shown. There is no evidence for the occurrence in NPD of abnormal fatty acids in sphingomyelins. 

Anilinonaphthalenesulfonic acid ammonia salt (ANS reagent) fatty acids [112,113] lecithin/sphingomyelin [114, 115] cholesterol and its esters [116, 117] steroids, detergents, hydrocarbons [118,119] prenol, prenylquinones [120]... 

Phospholipids are important constituents of cell membranes and are of two kinds. Glycerophospholipids, such as phosphatidylcholine and phos-phatidylethanolamine, are closely related to fats in that they have a glycerol backbone esterified to two fatty acids (one saturated and one unsaturaled) and to one phosphate ester. Sphingomyelins have the amino alcohol sphingo-sine for their backbone. 

FIGURE 12.4 (A) Diagrammatic representation of the separation of major simple lipid classes on silica gel TLC — solvent system hexane diethylether formic acid (80 20 2) (CE = cholesteryl esters, WE = wax esters, HC = hydrocarbon, EEA = free fatty acids, TG = triacylglycerol, CHO = cholesterol, DG = diacylglycerol, PL = phospholipids and other complex lipids). (B) Diagrammatic representation of the separation of major phospholipids on silica gel TLC — solvent sytem chloroform methanol water (70 30 3) (PA = phosphatidic acid, PE = phosphatidylethanolamine, PS = phosphatidylserine, PC = phosphatidylcholine, SPM = sphingomyelin, LPC = Lysophosphatidylcholine). 

PC = phosphatidylcholine, PE = phosphatidylethanolamine, PS = phosphatidylserine, PI = phosphati-dylinositol, Sph = sphingomyelin, FA = fatty acid, PA = phosphatidic acid, LPI = lyso-PI, CL = car-diolipin, LPC = Iyso-PC, CHO = cholesterol, CE = cholesterol ester, TG = triglycerides. 

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.

Figure 11.24 A summary of the reactions involved in synthesis of sphingomyelin. Reaction between serine and palmitoyl-CoA produces 3-oxosphinganine, which is converted to sphingamine. Attachment of a Long-chain fatty acid to the amino group of sphinganine produces dihydroxyceramide. Ceramide reacts with phosphatidylcholine the phosphocholine component forms an ester bond with the hydroxyl group at position one of ceramide.

The membrane contains 0.5-1.0% of the total lipid in milk and is composed principally of phospholipids and neutral lipids in the approximate ratio 2 1, with lesser amounts of other lipids (Tables 3.9 and 3.10) contamination with core lipid is a major problem. The phospholipids are principally phosphatidylcholine, phosphatidylethanolamine and sphingomyelin in the approximate ratio 2 2 1. The principal fatty acids and their approximate percentages in the phospholipids are Cl4 0 (5%), C16 0 (25%), C18 0 (14%), C,8 1 (25%), C18 2 (9%), C22 o (3%) and C24 0 (3%). Thus, the membrane contains a significantly higher level of polyunsaturated fatty acids than milk... 

Figure 3.2 The molecular arrangement of the cell membrane (A) integral proteins (B) glycoprotein (C) pore formed from integral protein (D) various phospholipids with saturated fatty acid chains (E) phospholipids with unsaturated fatty acid chains (F) network proteins (G) cholesterol (H) glycolipid (I) peripheral protein. There are four different phospholipids phosphatidyl serine phosphatidyl choline phosphatidyl ethanolamine and sphingomyelin represented as , o. The stippled area of the protein represents the hydrophobic portion. Source From Ref. 1.

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