VITAMIN AND GROWTH FACTOR RESEARCH 



unconjugated) form, and many investigators still have not 

 adjusted themselves to the changed situation but persist in speak- 

 ing of the "pyridoxine content" of foodstuffs (although in many 

 foodstuffs no detectable pyridoxine is present, all of the vitamin 

 Be being present as pyridoxal and pyridoxamine (49)) or of 

 "pyridoxine-deficient" rations (yeast, an excellent source of 

 vitamin Be, is pyridoxine-deficient — i.e., it contains little or no 

 pyridoxine* (49)). If accuracy in nomenclature is a prerequisite 

 to accuracy in thought, situations such as this, which occur fre- 

 quently in the vitamin field (cf. vitamin A vs. vitamin A activity, 

 folic acid vs. folic acid activity, etc.), should receive more 

 attention. The matter is not entirely academic, for whereas 

 pyridoxine is a very stable compound in foodstuffs, pyridoxal 

 because of its reactive carbonyl grouping is not, and it is possible 

 that an inaccurate nomenclature has contributed to the delay 

 in recognition of the destruction of vitamin Be that may occur 

 in food processing. 



Immediately following synthesis of pyridoxal, one coenzy- 

 matic form of vitamin Be was recognized by Gunsalus and co- 

 workers (19) to be pyridoxal phosphate (formula III); sub- 

 sequently pyridoxamine phosphate (formula IV) also was dis- 

 covered by Rabinowitz and Snell (48) . The latter product was 

 later found to serve as an essential growth factor for certain lactic 

 acid bacteria (e.g., Lactobacillus delbrueckii (34)), which cannot 



CHO CH2NH2 



HO [T^ CH2OPO3H2 HO |r^CH20P03H2 



HgClj^J HsCl^J 



(HI) Pyridoxal phosphate (IV) Pyridoxamine phosphate 



* This statement may appear in conflict with the reported isolation (32) 

 of pyridoxine from yeast. This procedure has not been reported in detail; in 

 answer to a query Professor Kuhn revealed that nitric acid was used through- 

 out this procedure, and volunteered the opinion that the pyridoxamine 

 originally present probably was converted (by nitrous acid) to pyridoxine 

 during the course of the isolation. Most other isolations of pyridoxine were 

 from rice-bran extract, in which this form of vitamin Be predominates. 



93 



