240 PYRIDOXINE AND RELATED COMPOUNDS 



The purified coenzyme from synthetic sources contained one phosphoiTis 

 per mole of pyridoxal.^ In contrast to pyridoxal, there was no maximum ab- 

 sorption at 300 m/i in alkahne solution, which would eliminate the possi- 

 bility that the phosphate was at position 3. Similar conclusions were reached 

 in a direct chemical study. ^''' ^^ Nevertheless, strong claims'-'^^ were made 

 for the activity of the 3-phosphate which were resolved only by a direct 

 comparison of the various preparations under identical conditions. ^^' ^* 

 Chemical proof of structure^"^^- ^^'^^ including the preparation of a variety 

 of derivatives has now been given. From the data now available, pyridoxal 

 phosphate is unquestionably the monophosphoric acid ester of the 5-hy- 

 droxymethyl group of pyridoxal. A 4-phosphate2^ has been postulated to 

 account for some aspects of spectrum, but this possibility has been elimi- 

 nated.19-22 



B. FORMATION OF THE COENZYME FORM 



As mentioned, the only form of vitamin Be which is active enzymatically 

 is pyridoxal-5-phosphate. The other members of the vitamin Be groups owe 

 their activity to systems capable of converting them into pyridoxal-5-phos- 

 phate. The interrelationships are illustrated below. The conversion of pyri- 

 doxine, pyridoxal, and pyridoxamine into pyridoxal phosphate during 

 growth of organisms using these materials as sources of vitamin Be has 

 been demonstrated biologically.^"* The conversion of pyridoxal to its phos- 

 phate by an enzymatic reaction involving ATP^' ^^ has been studied. The 

 conversion of pyridoxamine phosphate to pyridoxal phosphate by way of 



8 J. Baddiley and E. F. Gale, Nature 155, 727 (1945). 



3 I. C. Gunsalus, W. W. Umbreit, W. D. Bellam}^ and C. E. Foust, /. Biol. Chem. 



161, 743 (1945). 

 10 I. C. Gunsalus and W. W. Umbreit, Ahstr. 110th Meeting Am. Chem. Soc. p. 34B 

 (1946). 



" D. Heyl, S. A. Harris, and K. Folkers, Abstr. 110th Meeting Am. Chem. Soc. (Chi- 

 cago), p. 35B (1946). 



12 P. Karrer, Schweiz. Z. Pathol, u. Bacteriol. 10, 351 (1947). 



13 P. Karrer, and M. Viscontini, Helv. Chim. Acta 30, 52 (1947). 

 " P. Karrer and M. Viscontini, Helv. Chim. Acta 30, 524 (1947). 



16 P. Karrer and M. Viscontini, Helv. Chim. Acta 30, 528 (1947). 



i« P. Karrer, M. Viscontini, and D. Forster, Helv. Chim. Acta 31, 1004 (1948). 



17 I. C. Gunsalus and W. W. Umbreit, J. Biol. Chem. 170, 415 (1947). 



18 W. W. Umbreit and I. C. Gunsalus, /. Biol. Chem. 179, 279 (1949). 



19 D. Heyl, E. Luz, S. A. Harris, and K. Follters, /. Am. Chem. Soc. 73, 3430 (1951). 

 2" D. Heyl and S. A. Harris, /. Am. Chem. Soc. 73, 3434 (1951). 



21 p. Heyl, E. Luz, S. A. Harris, and K. Folkers, J. Am. Chem. Soc. 73, 3436 (1951). 



22 D. Heyl, E. Luz, and S. A. Harris, /. Am. Chem. Soc. 73, 3437 (1951). 



23 J. Baddiley, E. M. Thain, and A. W. Rodwell, Nature 167, 556 (1951). 



2' I. C. Gunsalus, W. I). Bellamy, and W. W. Umbreit, J. Biol. Chem. 160, 461 (1945). 

 26 W. W. Umbreit and J. G. Waddell, Proc. Soc. Exptl. Biol. Med. 70, 293 (1949). 



