V. SPECIFICITY OF ACTION 443 



The methionine requirement of chicks for growth was found to be in- 

 creased by deficiencies of either vitamin B12 or folic acid.'^^ 



G. VITAMIN B12 AND TUMORS 



Woolley^-® has observed thai spontaneous mammary tumors of mice 

 may possess the ability to synthesize vitamin B12 . This ability of the can- 

 cerous tissue would be a distinct difference from normal mouse tissue and 

 would constitute an important clue to the etiology and the treatment of at 

 least this particular type of tumor. It was noted that the nursing young 

 from tumor-bearing mothers gained normally on a vitamin Bi2-deficient 

 ration, whereas the young from non-tumorous mothers gained at a slower 

 rate recognized to be due to vitamin B12 deficiency. The fact that only 

 spontaneous tumors appeared to synthesize vitamin B12 , whereas trans- 

 planted tumors did not, somewhat complicates the interpretation of the 

 observed phenomenon. 



V. specificity of Action 



DONALD E. WOLF and KARL FOLKERS 



In discussing the specificity of action of vitamin B12, some limitations 

 must be made, since the title could include a broad review of all functions 

 of the vitamin in human, animal, and microbial metabolism. The treatment 

 presented here is intended to give a general survey of the subject and is 

 therefore not complete. 



A. ANIMAL AND MICROBIOLOGICAL METABOLISM 



Vitamin B12 has been found to affect the phosphorus metabolism of 

 Lactobacillus leichmannii} When this organism was grown in a medium 

 containing radioactive phosphorus, vitamin B12 was found to increase the 

 uptake of phosphorus in the desoxyribonucleic acid fraction of the cell to 

 a more pronounced extent than in the total cell or in the acid-insoluble 

 portion. This observation is in accord with the concept previously sug- 

 gested- that vitamin B12 is involved in nucleic acid synthesis. 



Extensive experiments have been carried out to demonstrate the effect 



"* T. H. Jukes, Paper presented at 124th Meeting of the American Chemical Society, 



Chicago, September, 1953. 

 1" D. W. Woolley, Proc. Natl. Acad. Sci. U. S. 39, 6, 1953. 



> I. Z. Roberts, R. B. Roberts, and P. H. Abelson, J. Bacteriol. 58, 709 (1949). 



2 W. Shive, J. M. Ravel, and R. E. Eakin, J. Am. Chem. Soc. 70, 2614 (1948). 



