Flavoprotein


Also found in: Dictionary, Medical, Wikipedia.
Related to Flavoprotein: flavin, dehydrogenase, cytochrome, ubiquinone

flavoprotein

[¦fla·vō¦prō‚tēn]
(biochemistry)
Any of a number of conjugated protein dehydrogenases containing flavin that play a role in biological oxidations in both plants and animals; a yellow enzyme.

Flavoprotein

 

(also flavin enzyme or yellow enzyme), any one of a group of complex enzymes, whose riboflavin derivatives—flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN)—serve as prosthetic groups (non-protein components). Flavoproteins were discovered in 1932 by O. Warburg.

The prosthetic group of many flavoproteins contains, in addition to flavin nucleotides, metals (Fe, Cu, Mo), sulfur compounds, and other compounds. The metals are complexly bound to the flavin nucleotides. When in an oxidized state, most flavoproteins are colored yellow and have characteristic absorption bands in the ranges 350–380 and 450–460 nanometers; in a reduced state, they are colorless. Flavoproteins are related to the oxidoreductase class and catalyze important oxidation-reduction reactions in living organisms with the direct participation of FAD and, more rarely, FMN. The specificity (selectivity) and effectiveness of the action of flavoproteins are determined by the nature of their protein components (apoenzymes), which have still not been adequately studied. Most flavoproteins are associated with cell membranes, forming strong complexes with lipids that are part of their composition.

The primary function of flavoproteins is the oxidation of reduced nicotinamide adenine dinucleotide in electron transfer chains (seeOXIDATIVE PHOSPHORYLATION). Flavoproteins are also capable of directly oxidizing various substrates and detaching from them hydrogen atoms, which are then transferred onto oxygen either immediately (for example, xanthine oxidase) or through the chain of transfer of electrons (for example, succinate dehydrogenase).

Flavoproteins are abundant in nature; they participate in the catabolism of major classes of organic compounds in the cells of animals, plants, and microorganisms.

REFERENCE

Lehninger, A. Biokhimiia. Moscow, 1976. (Translated from English.)

N. N. CHERNOV

References in periodicals archive ?
FAD is used as a cofactor for most flavoproteins. Riboflavin deficiency would be expected cause disturbances in certain steps of metabolism.
Loss of mitochondrial integrity is another feature of cells undergoing apoptotic duress and is reflected in the spatial redistribution of the flavoprotein, AIF (apoptosis inducing factor) [22].
Reactive oxygen species generation by human spermatozoa is induced by exogenous NADPH and inhibited by the flavoprotein inhibitors diphenylene iodonium and quinacrine.
The proteins belonging to this group are ferredoxins, which represent the iron-sulphur cluster that performs the intermediate step in the electron transfer chain, transferring electrons from the flavoprotein to the terminal dioxygenase (Bertini et al., 1996).
300 [micro]L of Krebs-HEPES buffer, containing lucigenin (5 [micro]M) with and without the flavoprotein inhibitor diphenylene iodonium (DPI, 1 [micro]M) to inhibit NADPH oxidase, was placed into a 96-well OptiPlate, which was loaded into a POLARstar Optima photon counter (BMG Labtech, Melbourne, VIC, Australia) to measure background photon emission at 37[degrees]C.
B2 is needed to create the essential flavoprotein coenzymes for synthesis of L-methylfolate--the active form of folate--and for proper utilization of B6.
The enzyme responsible for the first step is an acyl-CoA dehydrogenase, which transfers the electrons to an electron-transfer flavoprotein (ETF) and Coenzyme Q of the respiratory chain by using a second flavoprotein ETF: CoQ oxidorreductase, also named ETF dehydrogenase.
En la mayoria de los casos estas alteraciones se deben a la deficiencia de una de las tres proteinas necesarias a saber: subunidades alfa o beta de la flavoproteina de transferencia de electrones (ETF; OMIM #231680 y 130410, respectivamente; ETF: por la sigla en ingles de electron transfer flavoprotein. OMIN: por la sigla en ingles de Online Mendelian Inheritance in Man) o de la ubiquinona-oxidorreductasa de la flavoproteina de transferencia de electrones (ETF-QO: por la sigla en ingles de electron transfer flavoprotein-Q coenzyme; OMIM #231675), aunque en algunos pacientes obedecen a alteraciones no identificadas todavia del metabolismo de la riboflavina (1-3).
In many migratory animals, the light-sensitive chemical reactions involving the flavoprotein cryptochrome (CRY) are thought to play an important role in the ability to sense the Earth's magnetic field.
A promising candidate radical pair comprises the reduced flavin cofactor (FAD) and an oxidized tryptophan residue in a cryptochrome flavoprotein (Solov'yov et al., 2007; Ritz et al., 2000; Liedvogel et al., 2007).
Other potential orbital antigens include thyroglobulin and cholinesterase epitopes, the flavoprotein subunit of the mitochondrial succinate dehydrogenase, a 55 kDa protein (G2s), calsequestrin and others (8-11).
electron transport: Successive passage of electrons from one cytochrome or flavoprotein to another by a series of oxidation-reduction reactions.