FAD

FAD
Identifiers
CAS number	146-14-5 Y
PubChem	703
MeSH	Flavin-Adenine+Dinucleotide
Properties
Molecular formula	C27H33N9O15P2
Molar mass	785.55
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

This article relies largely or entirely upon a single source. Please help improve this article by introducing appropriate citations of additional sources. (May 2009)

In biochemistry, flavin adenine dinucleotide (FAD) is a redox cofactor involved in several important reactions in metabolism. FAD can exist in two different redox states and its biochemical role usually involves changing between these two states. Many oxidoreductases, called flavoenzymes or flavoproteins, require FAD as a prosthetic group which functions in electron transfers. FADH is known as reduced flavin adenine dinucleotide.

FAD is derived from riboflavin (vitamin B₂). It consists of a riboflavin group bound to the phosphate group of an adenosine diphosphate molecule. Note that, though the name flavin adenine dinucleotide is a misnomer (the molecule contains only one nucleotide, the riboflavin moiety is not linked to the D-ribityl group through glycosidic bond),^[1] it is generally accepted now.

FAD can be reduced to the FADH₂, whereby it accepts two hydrogen atoms:

The reduced coenzyme FADH₂ is an energy-carrying molecule, and it can be used as a substrate for oxidative phosphorylation in the mitochondria. FADH₂ is reoxidized to FAD, which produces enough of a proton gradient across the inner mitochondrial membrane for the enzyme ATP synthase to produce 2.0 equivalents of the high-energy compound ATP. The primary sources of reduced FAD in eukaryotic metabolism are the citric acid cycle and the beta oxidation reaction pathways. In the citric acid cycle, FAD is a prosthetic group in the enzyme succinate dehydrogenase that oxidizes succinate to fumarate, whereas in beta oxidation it serves as a coenzyme in the reaction of acyl CoA dehydrogenase.

References

The flavoprotein is the alpha-ketoglutarate dehydrogenase and the pyruvate dehydrogenase enzymes in the citric acid cycle, not the succinate dehydrogenase.

Additional images

Riboflavin

FADH2

Adenine

See also

• Flavin mononucleotide
• NAD

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