VI. BIOGENESIS 49 



completely. In this category are arsenocholine, phosphocholine, and tri- 

 ethylcholine. Following the administration of the arsenic and phosphorus 

 analogs of choline, Welch'" noted lipotropic activity and, in the case of 

 arsenocholine, demonstrated its presence in tissue phospholipid.'-' '^ Similar 

 findings for triethylcholine were reported })y McArthur.^^' ^^ It is natural to 

 ascribe the lipotropic effect of these compounds to their corresponding 

 phospholipid forms, l)ut the certainty of such an assumption remains to be 

 proved. Caution in this respect is required because of the possibility of 

 unrecognized biological properties of acetycholine or of other derivatives 

 of choline. That triethylcholine, for instance, may exhibit activity as an 

 antagonist of choline has been reported.^** 



VI. Biogenesis 



WENDELL H. GRIFFITH and JOSEPH F. NYC 



The biogenesis of choline in the animal organism, discussed in a pre- 

 ceding section, depends on dietary sources of vitamins such as folic acid 

 and Bi2 which may be rec^uired as cof actors in its enzymatic formation. 

 Limited synthesis occurs under advantageous dietary conditions in the rat 

 and chick, the two species used most commonly in choline studies. Severe 

 deficiencies result on diets low in labile methyl and in the vitamins in 

 question even though the diet may appear quite adequate in other respects. 

 On the other hand, unlimited synthesis characterizes the growth of most 

 microorganisms and plants. 



Pneimiococci^ • - and artificially produced mutant strains of Neurospora^- ^ 

 are the only forms known to require external supplies of choline for normal 

 growth. Choline and homocystine can replace methionine for the growth 

 of L. casei^ but not of E. coli.^ In preliminary experiments designed to 

 develop a microbiological assay for choline. Badger'^ found that amino- 

 ethanol would support the growth of a strain of pneumococcus in the 

 aljsence of choline. Other compounds which are related to choline and 

 aminoethanol were then tested for their activity in promoting growth of 



36 C. S. McArthur, Science 104, 222 (1946). 



" C. S. McArthur and C. C. Lucas, Biochem. J. 46, 226 (1950). 



38 A. S Keston and S. B. Wortis, Proc. Soc. Exptl. Biol. Med. 61, 439 (1946). 



1 L. Rane and Y. SubbaRow, J. Biol. Chem. 134, 455 (1940). 



2 E. Badger, /. Bacieriol. 47, 509 (1944); ./. Biol. Chem. 153, 183 (1944). 



3 N. H. Horowitz and G. W. Beadle, J. Biol. Chem. 150, 325 (1943). 



* N. H. Horowitz, D. Bonner, and M. B. Houlahan, J. Biol. Chem. 159, 145 (1945). 



6 R. J. Evans, Arch. Biochem. 16, 357 (1948). 



« M. N. Green and M. G. Sevag, Arch. Biochem. 9, 129 (1946). 



