432 VITAMIN Bi2 



tempting but at present fruitless to speculate that CF might be the postu- 

 lated coenzyine formed from folic acid and p-aminobenzoic acid as sug- 

 gested above. There is no evidence that CF will replace p-aminobenzoic 

 acid as a bacterial growth factor. Vitamin B12 wall not replace CF as a 

 growth factor for Le. ciirovorum^^ or as a detoxifying agent for the folic 

 acid antagonists,^^ and in turn CF will not replace vitamin B12 as a growth 

 factor for L. leichmannii^^ or chicks.^^ Ascorbic acid rather than vitamin B12 

 appears to be involved in the urinary excretion of increased amounts of 

 CF following the administration of folic acid.*^- ^^ 



Separate roles in certain microorganisms for vitamin B12 and CF, re- 

 spectively, in the formation of desoxyribosides and in their methylation 

 were suggested by Jukes and coworkers. ^^ Any of several purine and 

 pyrimidine desoxyribosides could replace vitamin B12 as a growth factor for 

 L. leichmannii, but only thymine desoxyriboside would replace CF for 

 growth of Le. citrovorum. 



F. RELATION OF VITAMIN Bi2 TO THE METABOLISM 

 OF CHOLINE AND METHIONINE 



1. In Chicks 



A borderline deficiency of methionine was recognized as being the first 

 limiting amino acid deficiency in soybean meal in diets for chicks, even 

 when the soybean meal was suitably heated so as to make its protein content 

 nutritionally available. ^°'^"^ Sardine or herring fish meal were also noted to 

 improve growth markedly when added to such diets, ^^"^^ and the suggestion 

 was made by Bird and Mattingly that there might exist in fish meal a 



83 H. E. Sauberlich, Federation Proc. 8, 247 (1949). 



8* H. P. Broquist, E. L. R. Stokstad, C. E. Hoffman, M. Belt, andd T. H. Jukes, 



Proc. Soc. Exptl. Biol. Med. 71, 549 (1949). 

 " H. E. Skipper, J. B. Chapman, and M. Bell, Cancer Research 11, 161 (1951). 

 86 T. H. Jukes, H. P. Broquist, and E. L. R. Stokstad, Arch. Biochem. 26, 157 (1950). 

 8' T. H. Jukes and coworkers, Unpublished investigations. 

 88 C. A. Nichol and A. D. Welch, Proc. Soc. Exptl. Biol. Med. 74, 52 (1950). 

 8»H. P. Broquist, E. L. R. Stokstad, and T. H. Jukes, /. Lab. Clin. Med. 38, 95 



(1951). 

 90 J. W. Hayward and F. H. Hafner, Poultry Sci. 20, 139 (1941). 

 «i H. J. Almquist, E. Mecchi, F. H. Kratzer, and C. R. Grau, J. Nutrition 24, 385 



(1942). 

 92 J. A. Marvel, C. W. Carrick, R. E. Roberts, and S. M. Hauge, Poultry Sci. 23, 



294 (1944). 

 " J. B. Christiansen, H. J. Deobald, J. G. Halpin, and E. B. Hart, Poultry Sci. 19, 



18 (1940). 

 "< J. S. Carver and R. J. Evans, U. S. Egg Poultry Mag. 49, 468 (1943). 

 " J. C. Hammond and H. W. Titus, Poultry Sci. 23, 49 (1944). 



