551 



Pteridines and Flavines 



CH.NHj 



\ 

 NH 



NH 

 / \ 

 CH, CHO 



O C 



\ 

 NH 



P— O— CH, 



"Active Formate" 



P— 0~CH, 



OH OH 



Glycineamide 

 Ribotide 



and 



OH OH 



Formylglycineamide 



Ribotide 



O 



II 



c 



HoN 



-N 



II 

 CH 



H2N 



P— O— CH, 



"Active 

 Formate" 



K® 



H,N 

 OHC 



P-O— CH, 



-N 

 CH 



HN 



OH OH 



5-Amino-4-imidazole- 

 carboxamide Ribotide 



OH OH 



5-Formamido-4-imidazole- 

 carboxamide Ribotide 



As was seen in the biosynthesis of histidine the N-1 and 

 C-2 atoms of the purine nucleus are donated to this amino 

 acid during its formation so that 



NH2 



N— 1 I 



N Y 



C— 2 



^^N^N 



Adenine 



Histidine 



indirectly, at least, these atoms too are furnished by the 

 coenzyme. 



