UNIDENTIFIED VITAMINS 75 



structure and synthesis studies were carried out in the Ledcrle Labora- 

 tories and the Calco Chemical Division of American Cyanamid. 



A comparison of the synthetic pteroylglutamic acid with natural vita- 

 min Be in the Parke-Davis Laboratories showed that these two factors 

 were identical (Table III). 



Structural studies showed that the fermentation L. casei factor con- 

 sists of three glutamic acid moieties in peptide linkage and attached 

 through the free amino group of the tripeptide to the carboxy group of 

 pteroic acid. The name pteroic acid was suggested for the acid : 



N N 



O 

 II 



<: 



HOC< \nHCH, 



N I 

 OH 



N 



The vitamin Be conjugate consists of seven glutamic acid moieties as 

 a heptapeptide attached similarly to pteroic acid. The nature of the 

 peptide linkages in the glutamic acid peptides has not been described 

 as yet (Table IV). 



The isolation of a polypeptide containing p-aminobenzoic acid from 

 yeast has been described. Analytical data showed that this peptide had 

 a free aromatic amino group, ten-eleven L-glutamic acid moieties and 

 an unknown amino acid moiety in a unit of the molecule. 



A functional relationship of the folic acid conjugates to this peptide 

 of p-aminobenzoic acid is not established but is an obvious possibility. 



The possible existence of other conjugates of pteroic acid containing 

 two, four, five, etc., moieties of glutamic acid appears even more pos- 

 sible after the announcement of this yeast peptide (Table V). 



It is evident that several factors which appear to be related chemi- 

 cally to pteroylglutamic acid remain for further chemical characteriza- 

 tion. These factors are the norite eluate factor, folic acid, Streptococcus 

 lactis R factor, vitamins Bio and Bn, factor R, and vitamin M. 



It does appear possible that some of these materials might have con- 

 tained one or more of the established pteroic acid conjugates of glutamic 

 acid or conjugates with a number of glutamic acid moieties other than 

 3 or 7 (Table VI). 



