ESMOND E. SNELL 



Utilize pyridoxal or pyridoxamine efficiently, and to serve also 

 as a coenzyme in enzymatic transamination (35). 



FOLIC AND FOLINIC ACIDS 



The tangled investigational threads that met in the isolation 

 and characterization of folic acid (formula V) have been traced 



.N^ ^N, 



CONHCHCOOH 

 I 

 CH2 



OH ^"2 



(V) Folic acid (Pteroylglutamic acid) 



elsewhere (54,57,44). Although the earliest observation of an 

 experimental deficiency of this substance was in monkeys 

 (vitamin M), the discovery failed to provide a practicable assay 

 procedure for its isolation. Such procedures were discovered 

 entirely independently, with chicks (vitamin Be) as the assay 

 organism in one instance, and lactic acid bacteria (eluate factor, 

 folic acid) in the other. The bacterial assays were used at one 

 or another stage in all of the successful isolations. 



All the organisms that respond to folic acid respond similarly 

 to folinic acid (formula VI). Thus, the original observations of 



CONHCHCOOH 



H,NrY^CH, O f' 

 N^^N^iH^ ^NH CH2 

 OH I GH2 COOH 



CHO 

 (VI) Folinic acid 



growth responses in various organisms to crude supplements 

 included the response to both substances. Some evidence in- 

 dicates that the amount of folinic acid in tissues surpasses the 

 amount of folic acid. To what extent the latter is an artifact, 

 formed from the more labile folinic acid (or the even more 



94 



