532 NIACIN 



tophan is used as efficiently as L-tryptophan for maintenance of nitrogen 

 balance and for plasma protein synthesis. i''^ 



d. In Man 



D-Tryptophan is apparently not utilized to any extent^ °^ for ordinary 

 metabolic purposes in man. Sarett and Goldsmith^^ could find no evidence 

 that D-tryptophan was used as a precursor of nicotinic acid in man. 



4. Tryptophan-Nicotinic Acid Relationships in Other Organisms 



a. Eggs 



It is well known that nicotinic acid is synthesized by the developing 

 chick^"^ and turkey^"^ embryo. There is also an increase in the total amount 

 of pyridine nucleotide as the embryo develops.^''^ The precursors of this 

 synthesized nicotinic acid are not known. However, Schweigert et al}^^ 

 found that tryptophan introduced into the embryo resulted in a moderately 

 increased synthesis of nicotinic acid. Kidder and associates"" were unable 

 to confirm this finding, although Denton and associates"^ were able to do 

 so. Furthermore, Ackermann and Taylor"^ have found that both nico- 

 tinamide and tryptophan can prevent toxicity from 3-acetylpyridine in the 

 developing embryo, although tryptophan was considerably less potent than 

 nicotinamide. These findings seem to indicate a tryptophan-nicotinic acid 

 relationship in this organism and have additional interest since this is a 

 situation in which tryptophan can apparently be converted to nicotinic 

 acid in the complete absence of any microorganisms. 



6. Plants 



The fact that plants can and do synthesize nicotinic acid during germi- 

 nation and growth from the simplest of inorganic elements is well known. 

 There is some evidence that tryptophan may serve as a precursor of nico- 

 tinic acid under certain conditions. Nason"' found that l- or DL-tryptophan 

 and 3-hydroxyanthranilic acid increased nicotinic acid synthesis in the 



"^ S. C. Madden, R. R. Woods, F. W. Shull, and G. H. Whipple, /. Exptl. Med. 79, 



607 (1944). 

 "5 A. A. Albanese and J. E. Frankston, /. Biol. Chem. 155, 101 (1944). 

 106 W. J. Dann and P. Handler, J. Biol. Chem. 140, 935 (1941). 

 "■^ C. Furman, E. E. Snell, and W. W. Cravens, Poultnj Sci. 26, 307 (1947). 

 i«8 M. Levy and N. F. Young, /. Biol. Chem. 176, 185 (1948). 



»»9 B. S. Schweigert, H. L. German, and M. J. Garber, /. Biol. Chem. 174, 383 (1948). 

 "0 G. W. Kidder, V. C. Dewey, M. B. Andrews, and R. R. Kidder, /. Nutrition 37, 



521 (1949). 

 "1 C. A. Denton, W. L. Kellogg, W. E. Rowland, and H. R. Bird, Arch. Biochem. and 



Biophys. 39, 1 (1952). 

 "2 W. W. Ackermann and A. Taylor, Proc. Soc. Exptl. Biol. Med. 67, 449 (1948) 

 "3 A. Nason, Science 109, 170 (1949); Am. J. Botany 8, 612 (1950). 



\ 



