VI. BIOGENESIS 521 



which is known to be easily and preferentially decarboxylated in the 2 

 position, forming nicotinic acid, and compounds which have been tested 

 principally by treating human pellagra, a difficult means of testing which 

 is subject to considerable clinical interpretation. The reported activity of 

 ornithine may be in a special category (p. 522). The reported activity of 

 isocinchomeronic acid seems very questionable. 



6. N'-substituted derivatives of nicotinic acid or nicotinamide may be 

 active or inactive, depending on the nature of the substituent group. The 

 reported inactivity of DPN is puzzling, since this substance is known to be 

 active in enzyme systems and for bacterial growth. This substance should 

 be retested, using more sensitive systems than acute canine blacktongue. 



7. Man, rat, and dog seem to have about the same ability to use various 

 types of nicotinic acid derivatives. 



The effectiveness of nicotinic acid derivatives in microorganisms has been 

 reviewed, elsewhere.^^- ^^"^^ 



B. TRYPTOPHAN AND DERIVATIVES 



The amino acid and some of its derivatives can replace nicotinic acid, 

 since many organisms possess the ability to convert tryptophan to nicotinic 

 acid. This subject is considered in Section VI. The principal compounds 

 of interest are listed in Table XII. Tryptophan can replace nicotinic acid 

 in human nutrition, ^^-^^ in the dog,^" and in many other species (p. 578), as 

 well as in the rat. 



VI. Biogenesis 



J. M. HUNDLEY 



A. DEMONSTRATION OF NICOTINIC ACID BIOSYNTHESIS 



It has long been known that certain mammals can synthesize nicotinic 

 acid. Several groups of investigators showed that rats thrive on diets which 

 produced pellagra in humans, blacktongue in dogs, and deficiency states 

 in pigs and monkeys. ^-^ Other investigators using various diets could dem- 



*^ L. M. Henderson, G. B. Ramasarma, and B. C. Johnson, J . Biol. Chem. 181, 731 



(1949). 

 " W. I. M. Holman and D. J. de Lange, Nature 165, 112 (1950). 

 fi^S. A. Singal, V. P. Sydenstricker, and J. M. Littlejohn, J. Biol. Chem. 176, 1051 



(1948). 

 » D. K. Miller and C. P. Rhoads, J. Clin. Invest. 14, 153 (1935). 

 2 T. W. Birch, H. Chick, and C. J. Martin, Biocheni. J. 31, 2065 (1937). 

 ' T. W. Birch, J. Nutrition 17, 281 (1939). 



