84 



THE BIOCHEMISTRY OF B VITAMINS 



Indeed, Bovarinck 37 has shown that if glutamic acid and asparagin are 

 boiled in aerated water containing a trace of manganous sulfate, the solu- 

 tion will manifest niacin activity. Niacin synthesis by rats is stimulated 

 by a mixture of glycine and dZ-8-amino-n-valeric acid. It is also known 

 that guvacine will substitute for nicotinic acid in the nutrition of 

 Staphylococcus aureus and Proteus vulgaris. A consideration of these facts 

 has led to the following proposed biosynthetic sequence: 



COOH 



CH 2 



CH 2 



Ah- 



-NH 2 

 I 

 COOH 



Glutamic acid 



H 2 C CH 2 



H 2 C CH— COOH 



V 



H 



« Proline 



CH 2 NH 2 



/ \ / 

 CH 2 CH 



CH 2 COOH 



NH 2 



Ornithine 



CH 2 



/ \ 



CH 2 CH 2 — coon 



CH 2 

 NH 2 



5-Amino-n-valeric acid 



CH 



CH 2 



CH 2 



CH— COOH H2O+ glycine 



-o 



-COOH 



NH 2 



Guvacine 



COOH 



Nicotinic acid 



Pantothenic Acid 



Pantothenic acid is required by, or is at least stimulative toward, a 

 relatively large proportion of the bacteria which have been tested. Thus, 

 Peterson and Peterson x list 52 bacteria having growth factor require- 

 ments which respond to pantothenic acid specifically, 2 which synthesize 

 it and 3 additional ones which do not require it. In another table they 

 list a total of nine bacteria which are reported to synthesize it. These 

 include the 5 organisms tested by Thompson, 5 all of which grow on rela- 

 tively simple media and produce other B vitamins, and Rhizobium meli- 

 lote 38 which grows in the root nodules of legumes. 



Despite the relatively small number of bacteria known to synthesize 

 pantothenic acid, there is good evidence on which to base the opinion that 

 bacterial synthesis is an important natural source. Its production has 

 been, demonstrated to take place, for example, in the rumen of sheep and 



