THE SPHINGOMYELINS 465 



readily hydrolyzable, while the NH — CO linkage is quite resistant to hy- 

 drolysis, it is possible to prepare such ceramides as palmityl and stearyl- 

 sphingosine; these had not previously been known. The properties of 

 some of these compounds are given in Table 11. 



Table 11 

 Melting Points and Solubilities of Some Sphingosine Fats and Some Ceramides"-* 



Melting Solubility 



point, 



Sphingosine °C. Ethanol Ether Chloroform Acetone Methanol 



0-Diacetvl 



lignoceryl- 70-71 + + + + + + + + + + + 



0-Dipalmitvl 



lignoceryl- 39-40 +(H) + + + + + + + + + 



0-Disteaiyl 



lignoceryl- 45-47 +(H) + + + + + + + + + 



0-Dibenzoyl 



lignoceryl- 57-58 ++(H) + + + + + + + + + + + + 



Tripalmitvl- 67-69 +(H) + + + + + + + + + + + + 



Tristearyl- 72-74 +(H) + + + + + + + + + + + + 



Tribenzoyl- 118-120 ++ + + + + + + + + + + + + 



Palmitvl- 86-87 ++ ++ ++(H) ++(H) 



Stearyl- 88-89 ++ ++ ++(H) ++(H) 



" +, slightly soluble; ++, fairly soluble; + + +, readily soluble; + + + +, very 

 soluble. H, soluble only in hot solvent. 



* Adapted from M. Reichel and S. J. Thannhauser, J. Biol. Chem., 135, 15-21 (1940). 



(7) Distribution of the Sphingomyelins 



Sphingomyelins are found with other phospholipids and cerebrosides in 

 highest concentration in the brain and nervous tissue. They also occur in 

 a relatively high proportion in kidneys and liver,^^^ spleen, ^-'^ and to some 

 extent in blood. ^^^ Sphingomyelin-like compounds have been prepared 

 from many other sources such as horse pancreas, *^^ kidneys and heart, ^""-^^^ 

 and the slimy skin secretion from the lamprey {Petromyzon fluviatilis^^'^) , 

 but not from the gastric mucosa of pigs.^*^ This substance is also found 

 in erythrocytes,^'''* suprarenals,'^"-*^^'^^^ sex organs,^"^ placenta, '°^ and in 

 traces in skeletal muscle. ^^^ The presence of sphingomyelin in erythrocytes 

 is denied by Haurovitz and Sladek,^^^ who believed that the supposed com- 

 pound \vas a mixture of lecithin and a cerebroside. Sphingomyelin or a 



3^» H. J. Channon and G. A. CoUison, Biochem. J., 23, 663-675 (1929). 



5« S. Frankel and T. R. Offer, Biochem. Z., 26, 53-54 (1910). 



3s» H. MacLean, Biochem. J., 6, 333-354 (1912). 



5*1 H. MacLean, Biochem. Z., 57, 132-142 (1913). 



=«2 J. Muller and H. Reinbach, Z. physiol. Chem., 92, 56-74 (1914). 



353 B. Uhnoo, Z. phijsiol. Chem., 256, 104-110 (1938). 



^' M. Burger and H. Beumer, Biochem. Z., 56, 446-456 (1913). 



^ D. L. Woodhouse, Biochem. J., 22, 1087-1096 (1928). 



366 H. Beumer, Arch, exptl. Path. Pharmakol, 77, 304-316 (1914). 



357 C. Sakali, Biochem. Z., 49, 317-325 (1913). 



3*8 F. Haurovitz and J. Slidek, Z. physiol. Chem., 173, 268-277 (1928). 



