VITAMINS, ANTIBIOTICS, AND GROWTH 



^ COOH 



COOH "^"2 



Aminoacrolein 

 fu marie acid 



COOH 



339 

 COOH 



OHC 



COOH 



COOH 



^ .COOH^ 



OHc' ^' 

 NHp 



Aminoacrolein 

 maleic acid 



or 



N 



Nicotinic 

 acid 



COOH 



Figure 3. Steps in the formation of nicotinic acid from 3-hydroxyanthranilic acid. 



Although tryptophan is an indispensable amino acid for animals, 

 microorganisms have an enzyme system, tryptophan synthetase, for 

 producing tryptophan from indole and serine. Indole can be produced 

 by the following pathway in E. coli: 



sedoheptulose 1, 7-diphosphate 



phosphoenolpyruvic acid -|- erythrose-4-phosphate > 



2-keto-3-desoxy-7-phospho-D-glucoheptonic acid > 



quinic acid > 5-dehydroshikimic acid > shikimic acid 



5-phosphoshikimic acid 



a COOH 

 NH ribose phosphate 

 indole glycerophosphate 



anthranilic acid + PRPP 





COOH 



NH - CH = COH(CHOH)2CH20Pi 



indole + glyceraldehyde phosphate 



The ability to produce tryptophan can thus be traced back to 

 aromatic biosynthesis through anthranilic acid, which is itself a product 

 of tryptophan metabolism or can be produced from shikimic acid. 

 Animals differ from non-dependent species, therefore, in lacking the 

 tryptophan synthetase system for biosynthesis of tryptophan, the pre- 

 cursor of nicotinic acid. 



The symptoms of pellagra and blacktongue are not accompanied 

 by a disappearance of the pyridine nucleotide coenzymes from the 

 tissues, although nicotinic acid promptly relieves these symtoms. 



Thiamine. The molecule of thiamine divides readily into two por- 

 tions : 2-methyl-4-amino-5-hydroxymethylpyrimidine and 4-methyl-5- 



