VI. BIOGENESIS 



523 



shown that a mixture of glutamic acid and asparagine (or glutamine) heated 

 in the presence of manganese and iron gives rise to nicotinamide. Elhnger 

 and Abdel Kader-^ have suggested that ornithine and glutamic acid may 

 be involved in nicotinic acid synthesis on the basis of experiments using 

 Escherichia coli. Guvacine will substitute for nicotinic acid in the nutrition 

 of Siaphylococcus aureus and Proteus vulgaris.^'' Nicotinic acid synthesis in 

 rats may be increased by DL-5-amino-n-valeric acid.-^ Hankes ei alP have 



COOH 

 I 

 CH2 



CH; 



I 

 CH-NH2 



I 



COOH 



Glutamic acid 



H2C 

 H,C^ 



CH2 

 I 

 CH-COOH 



H 



Proline 



H, 



H2C CH 



HjC^ COOH 

 NH, 



Ornithine 



NH, 



H 



H2C ^C-COOH 

 HzC^ ^CH2 

 H 



Guvacin 



HC 



I 



H 



H2C ^CH 



I I 



H.C. COOH 

 NH2 



A^-5-Amino- 

 pentenic acid 



^C-COOH 



Hj 



H2C CH. 



I I 



H2C. COOH 

 NH, 



6-Amino-7i- 

 valeric acid 



Nicotinic acid 

 Fig. 9. The ornithine scheme for nicotinic acid biosynthesis. (Adapted from 

 Williams.") 



reported that anthranilic acid and ornithine together can apparently sub- 

 stitute for nicotinic acid under certain dietary circumstances. 



2. Biosynthesis from Tryptophan 



The mechanism of mammalian nicotinic acid biosynthesis which is now 

 firmly established is conversion of the amino acid tryptophan to nicotinic 

 acid. A series of brilliant investigations beginning in 1945 have unraveled 



26 P. Ellinger and M. M. Abdel Kader, Biochem. J. 44, 285 (1949). 

 " R. J. Williams in The Biochemistry of the B Vitamins, American Chemical Society 

 Monograph No. 110, p. 84. Reinhold Publishing Corp., New York, 1950. 



28 J. W. Huff and W. A. Perlzvveig, /. Biol. Chem. 142, 401 (1942). 



29 L. V. Hankes, R. L. Lyman, and C. A. Elvehjem, J. Biol. Chem. 187, 547 (1950). 



