Flavin adenine dinucleotide

Bright orange solid


Soluble in water

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Flavin adenine dinucleotide ( FAD short ) is a coenzyme. It has an important role as electron carriers in various prokaryotic and eukaryotic metabolic processes such as oxidative phosphorylation, the β - oxidation of fatty acids and other redox reactions. FAD can single electrons transferred in contrast to NAD . Oxidoreductases can thus activate molecular oxygen by FAD.

Structure and chemical properties

FAD consisting of adenosine diphosphate, the riboflavin (vitamin B2) is associated. Alternatively, one could also say that it consists of adenosine monophosphate (AMP ) to which flavin mononucleotide ( FMN) is bound. The "reactive" nitrogen atoms are located in the isoalloxazine ring of the molecule.

The oxidized FAD is to include two protons (H ) and two electrons ( e-) in the reduced form FADH2 about: This is called an ECEC mechanism (s for electrochemical step c for chemical step of protonation ), the second protonation occurs only in sufficiently acidic solution. The transition between the ECE mechanism without the final transfer of a proton and the ECEC mechanism is also still dependent on the chemical environment: For free FAD in solution ECE and ECEC mechanism overlap at pH 6.7, is immobilized on surfaces FAD only reduced at about pH 9 according to the ECE mechanism.

The redox potential of FAD is located under standard conditions at -219 mV vs. NHE.

A solution of flavin adenine dinucleotide in water (10 g · l -1) has a pH value of about 6

Enzymes use FAD

The enzymes use FAD include:

  • Monoamine oxidase
  • Ferredoxin -NADP reductase
  • Glucose oxidase ( GOx )
  • Cellobiose dehydrogenase
  • Nitrate reductase
  • Pyruvate dehydrogenase
  • Acyl -CoA dehydrogenase