A report on Flavin adenine dinucleotide and Succinate dehydrogenase

Reaction of FAD to form FADH2
Solution NMR structure of protein NMA1147 from Neisseria meningitidis. Northeast structural genomics consortium target mr19
Approximate absorption spectrum for FAD
Image 5: Subunits of succinate dehydrogenase
Mechanism 1. Hydride transfer occurs by addition of H+ and 2 e−
Image 6: E2 Succinate oxidation mechanism.
Mechanism 2. Hydride transfer by abstraction of hydride from NADH
Image 7: E1cb Succinate oxidation mechanism.
Mechanism 3. Radical formation by electron abstraction
Image 8: Ubiquinone reduction mechanism.
Mechanism 4. The loss of hydride to electron deficient R group
Image 9: Electron carriers of the SQR complex. FADH2, iron-sulfur centers, heme b, and ubiquinone.
Mechanism 5. Use of nucleophilic addition to break R1-R2 bond
Mechanism 6. Carbon radical reacts with O2 and acid to form H2O2
Riboflavin
FADH{{sub|2}}

SdhA contains a covalently attached flavin adenine dinucleotide (FAD) cofactor and the succinate binding site and SdhB contains three iron-sulfur clusters: [2Fe-2S], [4Fe-4S], and [3Fe-4S].

- Succinate dehydrogenase

One well-known reaction is part of the citric acid cycle (also known as the TCA or Krebs cycle); succinate dehydrogenase (complex II in the electron transport chain) requires covalently bound FAD to catalyze the oxidation of succinate to fumarate by coupling it with the reduction of ubiquinone to ubiquinol.

- Flavin adenine dinucleotide
Reaction of FAD to form FADH2

5 related topics with Alpha

Overall
Overview of the citric acid cycle

Citric acid cycle

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Series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

Series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

Overview of the citric acid cycle
Structural diagram of acetyl-CoA: The portion in blue, on the left, is the acetyl group; the portion in black is coenzyme A.

The overall yield of energy-containing compounds from the citric acid cycle is three NADH, one FADH2, and one GTP.

FADH2 is covalently attached to succinate dehydrogenase, an enzyme which functions both in the CAC and the mitochondrial electron transport chain in oxidative phosphorylation.

The electron transport chain in the mitochondrion is the site of oxidative phosphorylation in eukaryotes. The NADH and succinate generated in the citric acid cycle are oxidized, which releases the energy of oxygen to power ATP synthase.

Electron transport chain

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Series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H+ ions) across a membrane.

Series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H+ ions) across a membrane.

The electron transport chain in the mitochondrion is the site of oxidative phosphorylation in eukaryotes. The NADH and succinate generated in the citric acid cycle are oxidized, which releases the energy of oxygen to power ATP synthase.
Photosynthetic electron transport chain of the thylakoid membrane.
Depiction of ATP synthase, the site of oxidative phosphorylation to generate ATP.

The energy released by reactions of oxygen and reduced compounds such as cytochrome c and (indirectly) NADH and FADH is used by the electron transport chain to pump protons into the intermembrane space, generating the electrochemical gradient over the inner mitochondrial membrane.

Complex I (NADH coenzyme Q reductase; labeled I) accepts electrons from the Krebs cycle electron carrier nicotinamide adenine dinucleotide (NADH), and passes them to coenzyme Q (ubiquinone; labeled Q), which also receives electrons from Complex II (succinate dehydrogenase; labeled II).

Two mitochondria from mammalian lung tissue displaying their matrix and membranes as shown by electron microscopy

Mitochondrion

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Double-membrane-bound organelle found in most eukaryotic organisms.

Double-membrane-bound organelle found in most eukaryotic organisms.

Two mitochondria from mammalian lung tissue displaying their matrix and membranes as shown by electron microscopy
Simplified structure of a mitochondrion.
Cross-sectional image of cristae in a rat liver mitochondrion to demonstrate the likely 3D structure and relationship to the inner membrane
Electron transport chain in the mitochondrial intermembrane space
Transmission electron micrograph of a chondrocyte, stained for calcium, showing its nucleus (N) and mitochondria (M).
Typical mitochondrial network (green) in two human cells (HeLa cells)
Model of the yeast multimeric tethering complex, ERMES
Evolution of MROs
The circular 16,569 bp human mitochondrial genome encoding 37 genes, i.e., 28 on the H-strand and 9 on the L-strand.

The enzymes of the citric acid cycle are located in the mitochondrial matrix, with the exception of succinate dehydrogenase, which is bound to the inner mitochondrial membrane as part of Complex II.

The citric acid cycle oxidizes the acetyl-CoA to carbon dioxide, and, in the process, produces reduced cofactors (three molecules of NADH and one molecule of FADH2) that are a source of electrons for the electron transport chain, and a molecule of GTP (which is readily converted to an ATP).

Biological roles of succinate. Inside the mitochondria, succinate serves as an intermediate in multiple metabolic pathways and contributes to the generation of ROS. Outside the mitochondria, succinate functions as both an intracellular and extracellular signaling molecule. OOA=oxaloacetate; a-KG=alpha ketoglutarate; GLUT= Glutamate; GABA = gamma-aminobutyric acid; SSA=Succinic semialdehyde ; PHD= prolyl hydroxylase; HIF-1a=hypoxia inducible factor 1a; TET= Ten-eleven Translocation Enzymes; JMJD3= Histone demethylase Jumonji D3

Succinic acid

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Dicarboxylic acid with the chemical formula 2(CO2H)2.

Dicarboxylic acid with the chemical formula 2(CO2H)2.

Biological roles of succinate. Inside the mitochondria, succinate serves as an intermediate in multiple metabolic pathways and contributes to the generation of ROS. Outside the mitochondria, succinate functions as both an intracellular and extracellular signaling molecule. OOA=oxaloacetate; a-KG=alpha ketoglutarate; GLUT= Glutamate; GABA = gamma-aminobutyric acid; SSA=Succinic semialdehyde ; PHD= prolyl hydroxylase; HIF-1a=hypoxia inducible factor 1a; TET= Ten-eleven Translocation Enzymes; JMJD3= Histone demethylase Jumonji D3
Amino acid sequence of GPR91. Succinate binds to GPR91, a 7-transmembrane G-protein coupled receptor, located on a variety of cell types. Red amino acids represent those involved in binding succinate. All other amino acids are colored according to their chemical properties (grey=nonpolar, cyan=negative charge, dark blue = positive charge, green=aromatic, dark purple=polar and noncharged, orange/light purple = special cases).
Accumulated succinate inhibits dioxygenases, such as histone and DNA demethylases or prolyl hydroxylases, by competitive inhibition. Thus, succinate modifies the epigenic landscape and regulates gene expression.

Catalyzed by the enzyme succinate dehydrogenase (SDH), succinate is subsequently oxidized to fumarate:

This enzyme complex is a 4 subunit membrane-bound lipoprotein which couples the oxidation of succinate to the reduction of ubiquinone via the intermediate electron carriers FAD and three 2Fe-2S clusters.

There are 18 key atoms in isoalloxazine that make up its characteristic three-ring structure. The R-group varies and differentiates various flavins.

Flavin group

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Common name for a group of organic compounds based on pteridine, formed by the tricyclic heterocycle isoalloxazine.

Common name for a group of organic compounds based on pteridine, formed by the tricyclic heterocycle isoalloxazine.

There are 18 key atoms in isoalloxazine that make up its characteristic three-ring structure. The R-group varies and differentiates various flavins.
Riboflavin
Equilibrium between the oxidized (left) and totally reduced (right) forms of flavin.
FAD
FMN

The flavin moiety is often attached with an adenosine diphosphate to form flavin adenine dinucleotide (FAD), and, in other circumstances, is found as flavin mononucleotide (or FMN), a phosphorylated form of riboflavin.

FADH2 is produced as a prosthetic group in succinate dehydrogenase, an enzyme involved in the citric acid cycle.