118 



A SYMPOSIUM ON RESPIRATORY ENZYMES 



In view of these results and the fact that cozymase is a monobasic 

 acid composed of its structural units minus five molecules of water, 

 the structural formula published in 1936 as a working hypothesis 

 (18) (see formula 9) seems well established. It remains, however, 

 to determine whether or not the pentose of the nicotinamide part is 

 identical with cZ-ribose. 



FORMULA 9 



N: 



H 



I 



■C- 



CONH. 



.<^ 



HC- 



C = C- 

 I I 



N N 



^C^ 



•N 

 II 

 C 

 I 

 NH. 



HC- 



HCOH 



I O 



HCOH 



I 

 HC 



O 



HCOH 



I 

 HCOH 



I 

 O HC 



O 



CH^O — P — O 



e 



— P-O-CH. 

 I 

 OH 



Concerning the structure of codehydrogenase II the following 

 results may be mentioned: Warburg and his co-workers stated that 

 the molecule consists of nicotinamide, adenine, two molecules of 

 pentose, and three molecules of phosphoric acid. These compounds 

 minus six molecules of water form the coenzyme. The experiments 

 on the linkage of the nicotinamide have already been mentioned. 

 In a very early stage of the work, Theorell, on the basis of cata- 

 phoretic experiments, claimed that the coenzyme is a tetrabasic acid 

 and that the amino group of the adenine is not free (19). Warburg, 

 Christian, and Griese (5) later revised this claim; their titration ex- 

 periments indicate that the coenzyme is a tribasic acid, and they 

 showed that the amino group is free. The finding of Adler and 

 Euler (7) that the enzymatic reaction Co I ^ Co II can take place 

 narrowed considerably the possibilities respecting the structure of 

 codehydrogenase IL The location of the third phosphoric acid group 

 now seems to be the only question concerning the structure that has 

 not been settled. The fact that cozymase contains adenosine diphos- 

 phate as an essential constituent suggested (15) that codehydrogenase 



