THE SPHINGOMYEMNS 455 



Althouo;li Tliudiclium-"- spparafed a fatty acid Avliich he called sphin- 

 gostearic acid from sphingomyelin, it is not probable that this product, 

 which had an empirical formula of CisHaeOa and a melting point of 57°C., 

 was a homogeneous substance. Sphingomyelin prepared by the older 

 methods from brain ;uid spleen was shown to yield j)almitic, stearic, and 

 lignoceric acids on hydrolysis. '"'•■''•'"•'''' Pyridine extraction has also been 

 used.^*'' Merz,"^ using an acetone fractionation method with brain phos- 

 pholipids, found that, in addition to these saturated acids, the unsaturated 

 acid nervonic acid was also present in sphingomyelin. The pi-esence of 

 palmitic acid in brain sphingomyelin appears questionable, since it has been 

 shown that sphingomyelin prepared by the earlier methods is a mixture 

 which contains hydrolecithin. Thannhauser and Boncoddo^" have re- 

 cently proved that brain sphingomj^elin has a different fatty acid composi- 

 tion from that prepared from other organs. Stearic, lignoceric, and ner- 

 vonic acids were sho\ATL to comprise the sole fatty acids in brain sphingomye- 

 lin, while palmitic and lignoceric acids are thg fatty acids present in lung 

 and spleen sphingomyelins.'^^ Hydrosphingosine occurred along with 

 sphingosine in the case of both brain and spleen sphingomyelins. Frankel 

 et al.^^^ prepared a sphingomj'-elin which contained sphingosine, choline, 

 phosphoric acid, and fatty acids in the expected proportions. There were 

 three fatt}^ acids present — palmitic, stearic, and lignoceric — which were 

 found in equivalent proportions. Frankel ei al. believe that sphingomyelin 

 consists of salt-like complexes which are formed by the condensation of sev- 

 eral single sphingomj^elin molecules by elimination of water through inter- 

 action of adjacent molecules of choline and phosphoric acid. It is believed 

 that such long-chain polyaminophospholipids may be of great importance 

 in producing the properties of irritabilit}^ and conductivity characteristic of 

 nerve tissue. 



a. Sphingomyelin Fatty Acid Ester. The possibility that sphingo- 

 myelin may exist in nature, combined with a second fatty acid in ester 

 linkage on the hydroxyl group of the sphingosine which has usually been 

 considered to be free, has recently been revived by Thannhauser and Rei- 

 chel.'^'* These workers were able to demonstrate that, when spleen sphingo- 

 myelin was hydrolyzed with a liver enzyme or with a purified pancreatic 

 lipase, palmitic acid could be isolated, in addition to choline, phosphoric 

 acid, and lignocerylsphingosine. "\Mien the Henriques method of alkaline 



"3 p. A. Levene, J. Biol. Chem., 15, 153-154 (1913). 



"* P. A. Levene, /. Biol. Chem., 18, 453-462 (1914). 



"« O. Rosenheim and M. C. Tebb, /. Physiol, 41, Proc, i-ii (1910-1911). 



3'« W. Merz, Z. physiol. Chem., 1.93, 59-87 (1930). 



^" S. J. Thannhauser and N. F. Boncoddo, /. Biol. Chem., 172, 141-147 (1948). 



"* S. J. Thannhauser, J. Benotti, and N. F. Boncoddo, /. Biol. Chem., 166, 677-681 

 (1946). 



"»E. Frankel, F. Bielschowskv, and S. J. Thannhauser, Z. physiol. Chem., 218, 1-11 

 (1933). 



