48 



CHOLINE 



other amino acids appear unable to serve as methyl donors (Table V). 

 Furthermore, sulfocholine is also negative in this respect, despite the great 

 activity of similar sulfur methyl groups in the thetins. 



As far as is known, the attribute of being a methyl donor also confers 

 on a molecule the function of serving as a precursor of the methyl portion 



TABLE VI 

 Biological Activity of Various N-Alkyl and Related Compounds 



In presence of betaine and B12 . 

 In presence of B12 . 



of choline. On the other hand, derivatives of choline are known that may 

 be used in the synthesis of lecithin but lack the methyl donor characteristic 



28 C. H. Best and M. E. Huntsman, ./. Phijsiol. (London) 75, 405 (1932). 

 2^ T. H. Jukes, cited by A. W. Moyer and V. du Vigneaud, ref. 1. 

 3° H. E. Carter and D. B. Melville, /. Biol. Chem. 133, 109 (1940). 

 '1 C. H. Best and J. H. Ridout, Ann. Rev. Biochem. 8, 349 (1939). 



32 M. E. H. Mawson and A. D. Welch, Biochem. J. 30, 417 (1936). 



33 A. E. Schaefer, W. D. Salmon, and D. R. Strength, /. Nutrition 44, 305 (1951). 



3^ V. du Vigneaud, S. Simmonds, J. P. Chandler, and M. Cohn, J . Biol. Chem. 165, 



639 (1946). 

 3s V. du Vigneaud, J. P. Chandler, and A. W. Moyer, /. Biol. Chem. 139, 917 (1941). 



