Flavin adenine dinucleotide oxidoreductase

Gisi MR, L Xun (2003) Characterization of chlorophenol 4-monooxygenase (TftD) and NADH flavin adenine dinucleotide oxidoreductase (TftC) of Burkholderia cepacia ACllOO. J Bacteriol 185 2786-2792. 

Riboflavin (from the Latin flavus, yellow) serves in the metabolism as a component of the redox coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD see p. 104). As prosthetic groups, FMN and FAD are cofactors for various oxidoreductases (see p. 32). No specific disease due to a deficiency of this vitamin is known. 

Ferredoxin-NADP+ oxidoreductase 37 1 — — An enzyme containing one flavin adenine dinucleotide per molecule bound to outside of lamellae... 

The deprotonation and addition of a base to thiazolium salts are combined to produce an acyl carbanion equivalent (an active aldehyde) [363, 364], which is known to play an essential role in catalysis of the thiamine diphosphate (ThDP) coenzyme [365, 366]. The active aldehyde in ThDP dependent enzymes has the ability to mediate an efScient electron transfer to various physiological electron acceptors, such as lipoamide in pyruvate dehydrogenase multienzyme complex [367], flavin adenine dinucleotide (FAD) in pyruvate oxidase [368] and Fc4S4 cluster in pyruvate ferredoxin oxidoreductase [369]. 

Both groups of reactions are found in bacteria (14), all higher animals (i5), and plants (16) however, oxidative phosphorylation is responsible for 90 % of the oxygen consumed (i 7). Oxidative phosphorylation is driven by the respiratory electron-transport system that is embedded in the lipoprotein inner membrane of eukaryotic mitochondria and in the cell membrane of prokaryotes. It consists of four complexes (Scheme I). The first is composed of nicotinamide adenine dinucleotide (NADH) oxidase, flavin mononucleotide (FMN), and nonheme iron-sulfur proteins 18,19), and it transfers electrons from NADH to ubiquinone. The second is composed of succinate dehydrogenase (SDH), flavin adenine dinucleotide (FAD), and nonheme iron-sulfur proteins (20), and it transfers electrons from succinate to ubiquinone 21, 22). The third is composed of cytochromes b and c, and nonheme iron-sulfur proteins (23), and it transfers electrons from ubiquinone (UQ) to cytochrome c 24). The fourth complex consists of cytochrome c oxidase [ferrocytochrome c 0 oxidoreductase EC 1.9.3.1 25)] which transfers electrons from cytochrome c to O2 26, 27). 

Due to high biocompability and large surface are of cobalt oxide nanoparticles it can be used for immobilization of other biomolecules. Flavin adenine FAD is a flavoprotein coenzyme that plays an important biological role in many oxidoreductase processes and biochemical reactions. The immobilized FAD onto different electrode surfaces provides a basis for fabrication of sensors, biosensors, enzymatic reactors and biomedical devices. The electrocatalytic oxidation of NADH on the surface of graphite electrode modified with immobilization of FAD was investigated [276], Recently we used cyclic voltammetry as simple technique for cobalt-oxide nanoparticles formation and immobilization flavin adenine dinucleotide (FAD) [277], Repeated cyclic voltammograms of GC/ CoOx nanoparticles modified electrode in buffer solution containing FAD is shown in Fig.37A. 

The simplest example of such reactions is the decarboxylation of pyruvate. Both model and enzyme studies have shown the intermediacy of covalent complexes formed between the cofactor and the substrate. Kluger and coworkers have studied extensively the chemical and enzymatic behavior of the pyruvate and acetaldehyde complexes of ThDP (2-lactyl or LThDP, and 2-hydroxyethylThDP or HEThDP, respectively) . As Scheme 1 indicates, the coenzyme catalyzes both nonoxidative and oxidative pathways of pyruvate decarboxylation. The latter reactions are of immense consequence in human physiology. While the oxidation is a complex process, requiring an oxidizing agent (lipoic acid in the a-keto acid dehydrogenases , or flavin adenine dinucleotide, FAD or nicotinamide adenine dinucleotide , NAD " in the a-keto acid oxidases and Fe4.S4 in the pyruvate-ferredoxin oxidoreductase ) in addition to ThDP, it is generally accepted that the enamine is the substrate for the oxidation reactions. 

Porter, T.D. and C.B. Kasper (1986). NADPH-cytochrome P-450 oxidoreductase Flavin mononucleotide and flavin adenine dinucleotide domains evolved from different flavoproteins. Biochemistry 25, 1682-1687. 

Oxidoreductase dehydrogenase and flavoenzymes. Nicotinamide adenine dinucleotide (NAD+)/nicotinamide adenine dinucleotide phosphate (NADF) and flavin mononucleotide (FMN)/flavin adenine dinucleotide (FAD) are the two major types of redox coenzymes. 

This is one of the few oxidoreductases which is conventionally used in the food industry and also in chemical analysis (see section 1.5). The enzyme catalyzes the oxidation of glucose to gluconolactone (that can spontaneously yield gluconic acid) by molecular oxygen which in the presence of water is reduced to hydrogen peroxide. The enzyme (E) requires the coenzyme flavin adenine dinucleotide (FAD) which acts as the electron transporter, according to ... 

Fig. 2.2 Evolutionary origins of the structures of NADPH-cytochrome P450 oxidoreductase POR) and the neuronal NOS (tiNOS) reductase domain cyan), shown by overlays of the ribbon struetures of Desulfovibrto vulgaris flavodoxin (Fid) and spinach ferredoxin-NADP-oxidoreductase FNK). a Structures of Fid and FNR. b POR with flavin mononucleotide FMN) and flavin adenine dinucleotide FAD) highlighted with red sticks. The...

Fig. 2.5 Top panel, a Model of a complex between P450 and NADPH-cytochrome P450 oxidoreductase (FOR). A complex of P450 (red) and Mol A of the hinge-deletion mutant of POR(ATGEE), denoted as PORT e [53]). the flavin mononucleotide (FMN) domain (blue) and flavin adenine dinucleotide (FAD) domain (yellow)] and an enlarged view showing the relative orientation of the EMN and heme, b and c Open-book representation of molecular surface at the interface of P450 (b) and the EMN domain of POR (c). Five salt-bridge pairs are shown with same let-...

Oxidoreductase enzymes include dehydrogenases, reductases, and oxidases that typically contain flavin adenine dinucleotide (FAD), nicotinamide adenine dinucleotide phosphate (NAD(P)" ), or pyrroloquinohne quinone (PQQ) as redox cofactors. Although some specific enzymes possess cofactors with theoretically low redox potentials, this does not always translate to efficient performance when immobilized onto electrodes for BFCs. The caveat provides a need to study... 

Although some of the available riboflavin in natural foods may be present as the free vitamin, ready for intestinal transport, a larger fraction is present in the form of phosphorylated coenzymes FMN and flavin adenine dinucleotide (FAD), and there may also be very small amoimts of a gluco-side of the vitamin. These forms are all efficiently converted to free vitamin by enzymes secreted into the gut lumen, and they are therefore highly available for absorption. There are also small amounts of covalently bound forms of riboflavin, present in enzymes such as succinate dehydrogenase (succinate ubiquinone oxidoreductase EC 1.3.5.1), which cannot be released by the hydrolytic enzymes in the gut and are therefore unavailable for absorption. Also unavailable (or very poorly available) in man is the riboflavin synthesized by the gut flora of the large bowel. Certain animal species such as rodents can utilize this riboflavin source by coprophagy. 

Biochemical status estimates are generally based upon urinary excretion or measurements of erythrocyte glutathione reductase (NADPH oxidized glutathione oxidoreductase EC 1.6.4.2) and its reactivation with flavin adenine dinucleotide (FAD) in red cell lysates. Other biochemical indices, such as plasma or red cell flavin concentrations, have been less widely used, but their potential is increasing with the advent of new assay techniques such as capillary electrophoresis with highly sensitive laser-induced fluorescence detection. Fvmctional indices... 

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