608 THE BIOCHEMISTRY OF B VITAMINS 



these coenzymes in the nutrition of Hemophilus parainfluenzae. 3da Similar 

 results are obtained with Leuconostoc mesenteroides 9135 30a and with 

 Lactobacillus arabinosus 17-5, in which nicotinic acid largely exists as 

 coenzyme I. 55 



Most metabolites of nicotinic acid which are excreted in the urine of 

 animals are not effectively utilized by many organisms which require 

 nicotinic acid or nicotinamide for growth. Thus, trigonelline appears to be 

 inactive for most organisms; however, for Torula cremoris 2512 it is 

 almost as active as nicotinic acid. ISP-Methyl nicotinamide chloride has 

 only very slight ability to replace the nicotinic acid group for a few 

 organisms. Nicotinuric acid is utilized only with difficulty by many 

 organisms, but for some, e.g., Lactobacillus arabinosus, it is approximately 

 as active as nicotinic acid. 



Although nicotinuric acid was initially reported on the basis of a single 

 test to have a relatively high curative action in canine blacktongue, 24 it 

 has been proposed 26 on the basis of additional tests that the compound 

 probably should be grouped with pyrazinecarboxylic acid, 30 ' 31 pyrazine- 

 2,3-dicarboxylic acid, 30 ' 31 quinolinic acid, 30 3-aminopyridine, 56 2-amino- 

 nicotinic acid, 26 and pyrimidine-4-carboxylic acid. 20 These compounds do 

 not act regularly as blacktongue-preventives, but are sometimes able to 

 replace nicotinic acid, at least partially, in the diet of dogs for extended 

 periods. Nicotinuric acid administered to dogs maintained on a low 

 nicotinic acid diet is excreted almost quantitatively without metabolic 

 change. 57 This offers further evidence of the inability of the dog to utilize 

 this compound. It is also interesting that nicotinuric acid administered by 

 intravenous injection to human subjects was almost quantitatively ex- 

 creted unchanged in the urine. 58 



The majority of the biologically active analogues of nicotinic acid are 

 compounds which can be converted to the vitamin by the organism. How- 

 ever, the activities, even though of a low order, of thiazole-5-carboxylic 

 acid or its amide, thiazole-5-sulfonic acid, N-(2-pyridyl)-3-pyridinesul- 

 fonamide, pyrazinecarboxylic acid, and 2,3-pyrazinedicarboxylic acid can- 

 not be explained on this basis. It has been suggested that some of these 

 may actually be utilized as such without prior conversion to nicotinic acid. 



Administration of pyrazinecarboxylic acid and quinolinic acid was re- 

 ported to produce an increase in "V" factor activity in the blood and 

 urine of human subjects; 22 - 23 but this has not been verified by subse- 

 quent work, 30 in which a slightly different assay method for the "V" 

 factor was employed. Quinolinic acid, pyrazine monocarboxylic acid, or 

 pyrazine-2,3-dicarboxylic acid administered orally to male subjects did 

 not cause a rise in the "V" factor content of blood cells. Neither was 

 synthesis of "V" factor obtained on incubation of the three acids under 



