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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]
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 .
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:
Thus, the two substrates of this enzyme are ATP and riboflavin, whereas its two products are ADP and FMN. Riboflavin is converted into catalytically active cofactors (FAD and FMN) by the actions of riboflavin kinase (EC 2.7.1.26), which converts it into FMN, and FAD synthetase (EC 2.7.7.2), which adenylates FMN to FAD. Eukaryotes usually have ...
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 ...
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 + .
[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]
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 ...