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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/09/29 19:17:38」(JST)

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"FAD" redirects here. For other uses, see FAD (disambiguation).

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, which it converts between by accepting or donating electrons. The molecule consists of a riboflavin moiety (vitamin B₂) bound to the phosphate group of an ADP molecule. The flavin group is bound to ribitol, a sugar alcohol, by a carbon-nitrogen bond, not a glycosidic bond. Thus, riboflavin is not technically a nucleotide; the name flavin adenine dinucleotide is a misnomer.^[1]

FAD can be reduced to FADH₂, whereby it accepts two hydrogen atoms (a net gain of two electrons):

FAD (fully oxidized form, or quinone form) accepts two electrons and two protons to become FADH2 (hydroquinone form). FADH2 can then be oxidized to the semireduced form (semiquinone) FADH by donating one electron and one proton. The semiquinone is then oxidized once more by losing an electron and a proton and is returned to the initial quinone form (FAD).

FAD is an aromatic ring system, whereas FADH₂ is not. This means that FADH₂ is significantly higher in energy, without the stabilization that aromatic structure provides. FADH₂ is an energy-carrying molecule, because, if it is oxidized, it will regain aromaticity and release all the energy represented by this stabilization.

The primary biochemical role of FADH₂ in eukaryotes is to carry high-energy electrons used for oxidative phosphorylation. FAD is a prosthetic group in the enzyme complex succinate dehydrogenase (complex II) that oxidizes succinate to fumarate in the eighth step of the citric acid cycle. The high-energy electrons from this oxidation are stored momentarily by reducing FAD to FADH₂. FADH₂ then reverts to FAD, sending its two high-energy electrons through the electron transport chain; the energy in FADH₂ is enough to produce 1.5 equivalents of ATP^[2] by oxidative phosphorylation. Another metabolic source of FADH₂ is beta oxidation, where FAD serves as a coenzyme to acyl CoA dehydrogenase.

A flavoprotein is a protein that contains a flavin moiety, this may be in the form of FAD or FMN (Flavin mononucleotide) . There are many flavoproteins besides components of the succinate dehydrogenase complex, including α-ketoglutarate dehydrogenase and a component of the pyruvate dehydrogenase complex.

Additional images

Riboflavin
FADH2
Adenine

External links

FAD bound to proteins in the PDB

References

^ Metzler DE, (2001) Biochemistry. The chemical reactions of living cells, 2nd edition, Harcourt, San Diego
^ Stryer, (2006) Biochemistry

UpToDate Contents

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1. シェーグレン・ラルソン症候群 sjogren larsson syndrome

English Journal

Immobilization of glucose oxidase into a nanoporous TiO2 film layered on metallophthalocyanine modified vertically-aligned carbon nanotubes for efficient direct electron transfer.

Cui HF, Zhang K, Zhang YF, Sun YL, Wang J, Zhang WD, Luong JH.SourceDepartment of Bioengineering, Zhengzhou University, 100# Science Avenue, Zhengzhou 450001, PR China. Electronic address: hfcui@zzu.edu.cn.
Biosensors & bioelectronics.Biosens Bioelectron.2013 Aug 15;46:113-8. doi: 10.1016/j.bios.2013.02.029. Epub 2013 Feb 26.
Glucose oxidase (GOD) was adsorbed into a nanoporous TiO2 film layered on the surface of an iron phthalocyanine (FePc) vertically-aligned carbon nanotube (CNT) modified electrode. A Nafion film was then dropcast on the electrode's surface to improve operational and storage stabilities of the GOD-bas
PMID 23517827

Dissecting the kinetics of the NADP+-FADH2 charge transfer complex and flavin semiquinones in neuronal nitric oxide synthase.

Li H, Jamal J, Chreifi G, Venkatesh V, Abou-Ziab H, Poulos TL.SourceDepartment of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, USA; Department of Pharmaceutical Sciences, University of California, Irvine, CA 92697-3900, USA; Department of Chemistry, University of California, Irvine, CA 92697-3900, USA. Electronic address: hli@uci.edu.
Journal of inorganic biochemistry.J Inorg Biochem.2013 Mar 22;124C:1-10. doi: 10.1016/j.jinorgbio.2013.03.008. [Epub ahead of print]
Electron flow within the neuronal nitric oxide synthase reductase domain (nNOSrd) includes hydride transfer from NADPH to FAD followed by two one-electron transfer reactions from FAD to FMN. We have used stopped flow spectrometry to closely monitor these electron transfer steps for both the wild typ
PMID 23567464

Japanese Journal

FADおよびFADH2存在下におけるD-アスパラギン酸酸化酵素とD-アスパラギン酸のドッキングシュミレーション

小林佳奈,村上知之,吉田崇志,小田彰史,高橋央宜
東北薬科大学研究誌 58, 35-40, 2011-12
… On the other hand, it is reported that DDO with cofactor FADH2 can also form a complex with D-Asp. … in this study, computational docking between D-Asp and DDO was carried out with FAD or FADH2 as the cofactor. … The results of docking studies indicate that D-Asp can be recognized both by DDO with FAD and DDO with FADH2, and the difference in binding affinity between the oxidative and reductive states is caused by difference of hydrogen bonding patterns. …
NAID 110009512447

A Mechanistic Analysis of Enzymatic Degradation of Organohalogen Compounds

Kurihara Tatsuo
Bioscience, biotechnology, and biochemistry 75(2), 189-198, 2011-02-23
… The enzyme is unique in that it catalyzes the non-redox reaction in an FADH2-dependent manner. …
NAID 10027897237

Purification and Properties of Fumarate Reductase from Bakers Yeast

MURATSUBAKI Haruhiro,KATSUME Takuro
Agricultural and Biological Chemistry 46(12), 2909-2917, 1982
… Double-reciprocal plots of the reaction rate against the FADH2 and FMNH2 concentrations curved upwards. … The hill coefficient values and S0.5 for FADH2 and FMNH2 were estimated to be 1.6 and 0.21 μM, and 1.5 and 0.38μM, respectively. …
NAID 130000028178

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「FAD」

Flavin adenine dinucleotide
Identifiers
CAS number	146-14-5
PubChem	643975
UNII	ZC44YTI8KK
EC number	205-663-1
DrugBank	DB03147
KEGG	D00005
MeSH	Flavin-Adenine+Dinucleotide
ChEBI	CHEBI:16238
ChEMBL	CHEMBL1232663
Beilstein Reference	1208946
Gmelin Reference	108834
3DMet	B04619
Jmol-3D images	Image 1
	SMILES CC1=CC2=C(C=C1C)N(C3=NC(=O)NC(=O)C3=N2)C[C@@H]([C@@H]([C@@H](COP(=O)(O)OP(=O)(O)OC[C@@H]4[C@H]([C@H]([C@@H](O4)N5C=NC6=C5N=CN=C6N)O)O)O)O)O ;
	InChI InChI=1S/C27H33N9O15P2/c1-10-3-12-13(4-11(10)2)35(24-18(32-12)25(42)34-27(43)33-24)5-14(37)19(39)15(38)6-48-52(44,45)51-53(46,47)49-7-16-20(40)21(41)26(50-16)36-9-31-17-22(28)29-8-30-23(17)36/h3-4,8-9,14-16,19-21,26,37-41H,5-7H2,1-2H3,(H,44,45)(H,46,47)(H2,28,29,30)(H,34,42,43)/t14-,15+,16+,19-,20+,21+,26+/m0/s1 [PubChem]; Key: VWWQXMAJTJZDQX-UYBVJOGSSA-N [PubChem] ;
Properties
Molecular formula	C27H33N9O15P2
Molar mass	785.55 g mol−1
Appearance	White, vitreous crystals
log P	-1.336
Acidity (pKa)	1.128
Basicity (pKb)	12.8689
	(verify) (what is: /?); Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
	Infobox references

　　[★] フラビンアデニンジヌクレオチド flavin adenine dinucleotide

[0] Metzler DE, (2001) Biochemistry. The chemical reactions of living cells, 2nd edition, Harcourt, San Diego

[1] Stryer, (2006) Biochemistry

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案内

FADH2