TITK CEPHAIJNS 447 



at — 72"( ■., contaiiied llu> s;unc amount of this liaction as did cephalin pre- 

 pared by the usual manner. This does not preclude some enzyme action. 



In contradistinction to choline, which can be shown to be an intermediate 

 of lecithin, the presence of free colamine cannot be demonstrated in animal 

 or in plant tissues. It is possible that the activity of lecithinase C, by 

 which the nitrogenous base is set free, may be limited to lecithin. Under 

 such conditions, the phosphoric acid would not be split from ethanolamine, 

 and it could be expected that the ester of the nitrogenous base would appear 

 as a decomposition product. That such is the case is suggested by the 

 demonstration that colamine phosphate, H2N-CH2CH20-PO(OH)2, is 

 present to the extent of 36 milligram per cent of the fresh weight of human 

 malignant tumors, as well as to a maximum of 1 milligram per cent in pan- 

 creas, liver, cattle embryo, and human benign tumors. ^^'^ However, cola- 

 mine is quickly destroyed by liver perfusion so that it can no longer be de- 

 tected after 2 hours, ^^^-^^^ and this fact may account for the failure to de- 

 tect the free base in animal tissues. Another possibility arises that cola- 

 mine may be transformed to monomethylaminoethanol, CH3NH-CH2- 

 CH2OH, or even to dimethylaminoethanol, (CH3)2N-CH2CH20H. Such 

 compounds have been detected in tissues, and are believed to represent in- 

 termediate stages between ethanolamine and choline (or, in fact, between 

 phosphatidylethanolamine and lecithin). ^^^--^^ 



One of the difficulties in the determination of the proportion of phospha- 

 tidylethanolamine has been the lack of a satisfactory method for the quan- 

 titative determination of colamine. Although this base gives a character- 

 istic gold salt which has a composition represented by the formula C2H8- 

 NOAuCU, the formation is not a quantitative one. The determination of 

 free amino nitrogen furnishes a method for the estimation of colamine in the 

 absence of other primary amines, amino acids, or phosphatidylserine; how- 

 over, even if only phosphatidylethanolamine is present, it cannot be used to 

 determine the extent of the hydrolysis, as the reaction takes place in the un- 

 hydrolyzed phosphatide as well as in the hydrolysates. The gold salt pre- 

 cipitation procedure has been used in the Thierfelder-Schulze method, ^^^ 

 which was later modified by Levene and Ingvaldsen.^-^ 



Artom^^" recently proposed an analytical procedure which gives quanti- 

 tative results for ethanolamine and for serine, separately or when they are 

 mixed. Ethanolamine is quantitatively separated from serine by adsorp- 

 tion on Permutit, while the amino acid is not adsorbed. Ethanolamine is 

 subsequently eluted from the Permutit column with concentrated sodium 

 chloride solution. The ethanolamine can be determined in the eluate by 



«" E. L. Outhouse, Biochem. J., 31, 1459-1463 (1937). 



288 M. Guggenheim and W. Loffler, Biochem. Z., 74, 208-218 (191G). 



*«9 H. Tliierfelder and O. Schulze, Z. physiol. Chem., 96, 296-308 (1915-1910.) 



^ C. Artom, J. Biol. Chem., 157, 585-594 (1945). 



