CHEMISTRY OF NUCLEOSIDES AND NUCLEOTIDES 

 iCO-NH, 



183 



^N 



-OH 

 -OH 



OH 0- 



I I 

 CHj-O-P-O-P-OH 



II II 

 O 



XLVI 



Coenzyme III 



c. Flavin Adenine Dinucleotide (FAD) 



The coenzyme generally known as flavin adenine dinucleotide is not a 

 true dinucleotide, since one carbohydrate residue is not glycosidically 

 bound. It participates in oxidation-reduction reactions at a higher general 

 level than that for DPN. It is a derivative of riboflavin and gives adenine 

 and phosphoric acid on hydrolysis.^''* An unsubstituted amino group is 

 present since FAD can be deaminated with nitrous acid, and on careful 

 alkaline hydrolysis it gives adenosine-5'-phosphate. In acids it also gives 

 riboflavin-5'-phosphate.^''^ A formula for FAD in which the two phosphate 

 residue are joined together as a pyrophosphate (XLVII) is fully confirmed 

 by synthesis. 



— O 



OH OH 



OH OH 



-CH-CH-CH-CH-CHj-O-P-O-P-O-CHj-CH-CH-CH-CH^ 



-N, 



NH, 







XLVII 

 FAD 



OH OH OH 



Me 

 Me 



Nv^ .N. 







Riboflavin-5'-phosphate, which has coenzyme activity itself under certain 

 circumstances, has been synthesized by phosphorylation of riboflavin with 

 phosphoryl chloride-^^ • -^^ or from 2',3',4'-triacetylriboflavin.2^^ FAD has 



2« O. Warburg and W. Christian, Biochem. Z. 298, 150 (1938). 



"« E. P. Abraham, Biochem. J. 33, 543 (1939). 



"" R. Kuhn and H. Rudy, Ber. 68, 383 (1935). 



"« H. S. Forrest and A. R. Todd, J. Chem. Soc. 1950, 3295. 



»" R. Kuhn, H. Rudy, and F. Weygand, Ber. 69, 1543 (1936). 



