Flavins

Flavins

Flavins are a group of organic compounds based on pteridine, which are biologically significant due to their role as cofactors in various enzymatic reactions. They are derived from riboflavin (vitamin B2) and are essential for the metabolism of carbohydrates, fats, and proteins. Flavins are involved in redox reactions and are crucial for cellular respiration and energy production.

Structure

Flavins are characterized by their isoalloxazine ring system, which is a tricyclic structure. The most common flavins are riboflavin, flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD). These compounds differ in their side chains but share the same core structure.

Riboflavin

Riboflavin, also known as vitamin B2, is a water-soluble vitamin that serves as a precursor to FMN and FAD. It is composed of a ribitol moiety attached to an isoalloxazine ring.

Flavin Mononucleotide (FMN)

FMN is a phosphorylated derivative of riboflavin. It acts as a cofactor for various oxidoreductases, including NADH dehydrogenase in the electron transport chain.

Flavin Adenine Dinucleotide (FAD)

FAD is a more complex flavin that includes an adenine nucleotide. It is a cofactor for several important enzymes, such as succinate dehydrogenase and acyl-CoA dehydrogenase, playing a critical role in the citric acid cycle and fatty acid oxidation.

Biological Functions

Flavins are essential for a wide range of biological processes due to their ability to undergo reversible redox reactions. They participate in:

• Electron Transport Chain: Flavins are integral to the electron transport chain, where they facilitate the transfer of electrons from NADH and FADH2 to the respiratory chain, ultimately leading to ATP production.
• Oxidative Stress Response: Flavins are involved in the detoxification of reactive oxygen species (ROS) through their role in enzymes like glutathione reductase.
• Metabolism: They are crucial for the metabolism of carbohydrates, fats, and proteins, acting as cofactors for enzymes that catalyze oxidation-reduction reactions.

Clinical Significance

Deficiency in riboflavin can lead to ariboflavinosis, characterized by sore throat, redness and swelling of the lining of the mouth and throat, cracks or sores on the outsides of the lips (cheilosis) and at the corners of the mouth (angular stomatitis), and a swollen, magenta-colored tongue (magenta tongue).

Also see

• Riboflavin
• Electron Transport Chain
• Oxidative Phosphorylation
• Vitamin B Complex
• Redox Reactions