ESMOND E. SNELL 



also may occur naturally. In addition, there appear to occur 

 also conjugates of each of these compounds, that contain up to 

 (and possibly more than) six additional glutamic acid residues 

 and that vary in growth activity depending upon the number of 

 conjugated glutamic acid residues and the test organism. Which 

 if any, of these compounds represents the coenzyme form of the 

 vitamin is not known. The difficulty presented to the analyst by 

 the occurrence of a vitamin in so many forms is great, and the 

 problem of accurate and convenient assay has not been entirely 

 solved. 



PANTETHEINE PANTETHINE 



During an attempt to culture Lactobacillus bulgaricus in a 

 chemically defined medium this and a number of related organ- 

 isms were found to require an unidentified substance for growth. 

 Highly purified concentrates of the substance were prepared from 



CH3 



I 

 HOCH2C-CHOHCONHCH2CH2CONHCH2GH2SH 



GH3 



(VIII) Pantetheine 



CH3 

 HOCH2-G-CHOHCONHCH2CH2CONHCH2CH2S- 



CH3 



(IX) Pantethine 



O-CH2CH-CHCHOHCH-N \ 



0=P-OH 



^o. 



G=C 



/ V 



O PO3H2 N^ p-^^2 



I C— N 



0=P-OH GH3 H 



O-CH2-G-GHOHCONHGH2GH2GONHGH2GH2SH 



GH3 



(X) Goenzyme A 



96 



