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Flavin mononucleotide (FMN), or riboflavin-5′-phosphate, is a biomolecule produced from riboflavin (vitamin B 2) by the enzyme riboflavin kinase and functions as the prosthetic group of various oxidoreductases, including NADH dehydrogenase, as well as a cofactor in biological blue-light photo receptors. [1]
The flavin group is capable of undergoing oxidation-reduction reactions, and can accept either one electron in a two-step process or two electrons at once. Reduction is made with the addition of hydrogen atoms to specific nitrogen atoms on the isoalloxazine ring system:
The two electrons on reduced FAD (FADH 2) are transferred one at a time to FMN and then a single electron is passed from FMN to the heme of the P450. [ 24 ] The P450 systems that are located in the mitochondria are dependent on two electron transfer proteins: An FAD containing adrenodoxin reductase (AR) and a small iron-sulfur group containing ...
90 flavoproteins are encoded in the human genome; about 84% require FAD and around 16% require FMN, whereas 5 proteins require both. [4] Flavoproteins are mainly located in the mitochondria . [ 4 ] Of all flavoproteins, 90% perform redox reactions and the other 10% are transferases , lyases , isomerases , ligases .
[18] [19] An example is the oxidation of glutathione to glutathione disulfide, both of which form a redox buffering system in the cell between the endoplasmic reticulum and the cytoplasm. yFMO is localized in the cytoplasm in order to maintain the optimum redox buffer ratio necessary for proteins containing disulfide bonds to fold properly. [18]
In enzymology, an FMN reductase (EC 1.5.1.29) is an enzyme that catalyzes the chemical reaction FMNH 2 + NAD(P)+ ⇌ {\displaystyle \rightleftharpoons } FMN + NAD(P)H + H + The 3 substrates of this enzyme are FMNH2 , NAD + , and NADP + , whereas its 4 products are FMN , NADH , NADPH , and H + .
Oxidoreductases, enzymes that catalyze oxidation-reduction reactions, constitute Class EC 1 of the IUBMB classification of enzyme-catalyzed reactions. [2] Any of these may be called dehydrogenases, especially those in which NAD + is the electron acceptor (oxidant), but reductase is also used when the physiological emphasis on reduction of the substrate, and oxidase is used only when O 2 is the ...
Oxidative phosphorylation in the eukaryotic mitochondrion is the best-understood example of this process. The mitochondrion is present in almost all eukaryotes, with the exception of anaerobic protozoa such as Trichomonas vaginalis that instead reduce protons to hydrogen in a remnant mitochondrion called a hydrogenosome .