A report on Riboflavin and Flavin adenine dinucleotide

Chemical structure
Reaction of FAD to form FADH2
Cultures of Micrococcus luteus growing on pyridine (left) and succinic acid (right). The pyridine culture has turned yellow from the accumulation of riboflavin.
Approximate absorption spectrum for FAD
Mechanism 1. Hydride transfer occurs by addition of H+ and 2 e−
Mechanism 2. Hydride transfer by abstraction of hydride from NADH
Mechanism 3. Radical formation by electron abstraction
Mechanism 4. The loss of hydride to electron deficient R group
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}}

It is essential to the formation of two major coenzymes, flavin mononucleotide and flavin adenine dinucleotide.

- Riboflavin

Theorell confirmed the pigment to be riboflavin's phosphate ester, flavin mononucleotide (FMN) in 1937, which was the first direct evidence for enzyme cofactors.

- Flavin adenine dinucleotide
Chemical structure

3 related topics with Alpha

Overall
The succinate dehydrogenase complex showing several cofactors, including flavin, iron–sulfur centers, and heme.

Cofactor (biochemistry)

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Non-protein chemical compound or metallic ion that is required for an enzyme's role as a catalyst .

Non-protein chemical compound or metallic ion that is required for an enzyme's role as a catalyst .

The succinate dehydrogenase complex showing several cofactors, including flavin, iron–sulfur centers, and heme.
A simple [Fe2S2] cluster containing two iron atoms and two sulfur atoms, coordinated by four protein cysteine residues.
The redox reactions of nicotinamide adenine dinucleotide.

For example, the multienzyme complex pyruvate dehydrogenase at the junction of glycolysis and the citric acid cycle requires five organic cofactors and one metal ion: loosely bound thiamine pyrophosphate (TPP), covalently bound lipoamide and flavin adenine dinucleotide (FAD), cosubstrates nicotinamide adenine dinucleotide (NAD+) and coenzyme A (CoA), and a metal ion (Mg2+).

Vitamins can serve as precursors to many organic cofactors (e.g., vitamins B1, B2, B6, B12, niacin, folic acid) or as coenzymes themselves (e.g., vitamin C).

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 biochemical source is the vitamin riboflavin.

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.

Human GSR with bound glutathione and FADH

Glutathione reductase

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Enzyme that in humans is encoded by the GSR gene.

Enzyme that in humans is encoded by the GSR gene.

Human GSR with bound glutathione and FADH
General reaction catalyzed by glutathione reductase
Reduced glutathione reductase, glutathione peroxidase and glutathione interact to reduce hydrogen peroxide to water, in order to protect the cell from oxidative damage.
Graphical representation of overall reaction catalyzed by GR
GR catalytic cycle

Glutathione reductase functions as dimeric disulfide oxidoreductase and utilizes an FAD prosthetic group and NADPH to reduce one molar equivalent of GSSG to two molar equivalents of GSH:

Some patients exhibit deficient levels of glutathione activity as a result of not consuming enough riboflavin in their diets.