708 THE BIOCHEMISTRY OF B VITAMINS 



is provided by the fact that compounds which fail to function as methyl 

 donors such as arsenocholine, diethylmethylhydroxyethylammonium 

 chloride and homocholine, are active in preventing fatty livers in the 

 rat or perosis in the chick, whereas such methyl donors as betaine and 

 methionine do not prevent perosis in the chick. 



Choline has been found to be essential for the growth of certain strains 

 of pneumococci (Types I, II, V, VIII) . 8 A number of choline analogues 

 have been tested as growth factors for a Type III strain; 9 the results of 

 these tests are summarized in Table 48. Of the known functions of 

 choline in animal nutrition, its utilization in phospholipide formation 

 appears to be its most likely role in the metabolism of the pneumococcus, 

 since ethanolamine, diethanolamine and triethanolamine are also effective. 

 The activity of these compounds, together with the inactivity of methio- 

 nine, betaine, phosphorylcholine, etc., suggest that for this organism 

 choline does not have a significant role in transmethylation. 



Two mutant strains, No. 34486 and No. 47904, which arose from the 

 ultraviolet irradiation of a culture of wild type Neurospora crassa were 

 found 10 - n to require choline for growth in a medium which supported 

 the growth of the wild type organism. Both mutants also responded to 

 acetylcholine, arsenocholine, phosphorylcholine, dimethylaminoethanol, 

 dimethylethylhydroxyethylammonium chloride, diethylmethylhydroxy- 

 ethylammonium chloride, triethylcholine and methionine. The following 

 compounds were inactive for both mutants: betaine, creatine, sarcosine, 

 ethanolamine, neurine, diethylaminoethanol, dimethylamine, trimethyl- 

 amine and tetramethylammonium chloride. Of considerable interest is 

 the fact that mutant No. 34486 can utilize monomethylaminoethanol but 

 No. 47904 cannot; under suitable conditions, this compound accumulates 

 in the latter organism. 48 These results were considered to indicate that 

 methylaminoethanol is an intermediate in the synthesis of choline by 

 Neurospora and that the block in mutant No. 34486 precedes the forma- 

 tion of methylaminoethanol, whereas the block in mutant No. 47904 fol- 

 lows it. The structural specificity exhibited suggests that in Neurospora 

 the predominant function of choline depends on its acting as an intact 

 molecule rather than as a methyl donor. 



Inhibitors Related to Choline 



Triethylcholine. Keston and Wortis 50 reported in 1946 that even 

 though triethylcholine is lipotropic when fed in small quantities to rats, 

 the compound is acutely toxic when injected into mice. The toxicity is 

 completely prevented by the simultaneous injection of an equal weight 

 of choline chloride. It was further observed that the action of choline in 

 the contraction of isolated frog muscle is blocked by triethylcholine while 



