Flavinadenine dinucleotide

Riboflavin (vitamin B2) 6,7-dimethyl-9-(D-l-ribityl)isoalloxazine (63), was discovered as a coloring matter in milk in 1879, but its importance was not then realized. Deficiency causes lesions of the eye and of the angle of the mouth. Riboflavin is phosphorylated by adenosine triphosphate (ATP) to give riboflavin 5 -phosphate (flavinadenine mononucleotide, FMN) and then flavinadenine dinucleotide (FAD) (64 R = riboflavin). These function as prosthetic groups in a number of flavoproteins which are dehydrogenation catalysts by virtue of the oxidation-reduction properties of the isoalloxazine system. 

Adenosinpyrophosphorsaure. Der KoRNBERGsche Dinucleotid-Cyclus (s. Abb. 3) ist in der gleichen Art wie beim Flavinadenin-Dinucleotid (s. S. 162) auch fur Cozymase anzunehmen. Dabei kommt es nicht nur zu einer Kopplung zwischen Funktion und Abbau, sondern sogar zu einer solchen zwischen Funktion, Abbau, Aufbau und Pyrophosphat-anreicherung. 

Benzopteridines Flavinmononucleotide (FMN), flavinadenine dinucleotide (FAD) (D 10.4.3) Coenzymes and cosubstrates of oxido-reductases (C 2.2), in humans formed from riboflavin (vitamin B2)... 

The pyrophosphate bond of DPN is ruptured by an enzyme found in kidney particles and in potatoes. The potato enzyme has been purified over 750-fold and found also to cleave the pyrophosphate linkages of reduced DPN, TPN, flavinadenine dinucleotide, adenosine diphosphate, adenosine triphosphate, and thiamine pyrophosphate. 

This system differs from the one which phosphorylates adenosine, because here adenosine diphosphate can also act as a phosphate donor. The enzyme is inert with isoriboflavin, and it does not catalyze the synthesis of flavinadenine dinucleotide. However, it does phosphorylate arabityl flavin and dichloroflavin, both of which are vitamin antagonists. A preparation from the small intestine of rats carries out the same reaction, but is active only with ATP. ... 

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