V. SPECIFICITY OF ACTION 239 



the step ol conviMtinji; 3-hydroxykvnuieiiinc to 3-hydroxyaiithraiiili(' ucid"*^ 

 3. Pyiidoxal phosphate is concerned with the formation of tryptophan^" 

 by tho condensation of indole phis s(>rine.^' 



F. SULFUR-CONTAIXIXC; AMINO ACIDS AND PEPTIDES 



Pyridoxal phosphate is the coenzyme of the cj'stathionine cleavage to 

 homocysteine and serine.'-*- It is involved, as well, in the cysteine deaminase 

 by a process which may be identical with the cystathionine cleavage.^* '^^ 



V. specificity of Action 



W. W. UMBREIT 



A. COENZYME FORM 



Gunsalus and Bellamy ^'^ discovered that the rate of tyrosine decarboxy- 

 lation of Streptococcus faecalis cells was dependent upon the supply of "pseu- 

 dopyridoxine"^ in the growth medium. Cells grown in media deficient in 

 members of the vitamin Be group did not decarboxylate tyrosine, but the 

 resting cells could be activated with respect to this reaction by the addition 

 of pyridoxal.^ When enzyme preparations from such cells were employed, 

 adenosinetriphosphate (ATP) was necessary in addition to pj'ridoxal for 

 activation.^ It was possible to obtain active preparations of the coenzyme 

 in the absence of ATP by treatments designed to phosphorylate the pyri- 

 doxal.^ By purification of yeast fractions showing codecarboxylase activity, 

 a material was obtained which appeared to contain pyridoxal phosphate.'' 

 The biological properties of the compound were characterized by its acti- 

 vation of some enzyme systems listed previously, and in those cases studied 

 the natural material from yeast and the synthetic preparations were inter- 

 changeable."' ^ 



9» W. \V. Umbreit, VV. A. Wood, ami I. C. Gunsulus, J. Biol. Chem. 165, 731 (1946). 



8' E. L. Tatum and D. Boniior, Proc. Natl. Acad. Sci. 30, 30 (1944). 



82 F. Binkloy and G. M. Christensen, /. Am. Chem. Soc. 73, 3535 (1951). 



" A. E. Braushtein and R. M. Azarkh, Dnhlady Akad. Xauk. S. S. S. li. 71, 93 (1950) 



[C. A. 44, 7900 (1950)]. 

 9^ R. E. Kallio, /. Biol. Chem. 192, 371 (1951). 

 ' W. D. Bellamy and I. C. Gunsalus, J. Hacteriol. 46, 573 (1943). 



2 I. C. Gunsalu.s and W. D. Bellamy, J. Bacteriol. 47, 413 (1944). 



3 W. D. Bellamy and I. C. Gunsalus, J. Bacteriol. 48, 191 (1944). 



* 1. C. Gunsalus and W. I). Bellamy, J. Biol. Chem. 155, 557 (1944). 



^ 1. C. Gunsalus and W. 1). Bellamy, ./. Biol. Chem. 155, 357 (1944). 



6 I. C. Gunsalus, W. I). Bellamy, and W. W. I'mhieit , 7. Biol. Chem. 155, 6S5 (1945). 



' W. \\. I'mhreit, W. I). Bellamy, and I. C. Gunsalus, Arch. Biochcm. 7, 1S5 (1945). 



