Flavins adenine-diphosphate

In most organisms undergoing aerobic metabolism, pyruvate is oxidized to acetyl-CoA in a complex process involving its decarboxylation (Eq. 10-6). This oxidative decarboxylation, like the decarboxylation of pyruvate to acetaldehyde, requires thiamin diphosphate. In addition, an array of other catalysts participate in the process (see Fig. 15-15). Among these are the electron carrier flavin adenine diphosphate (FAD), which is derived from the vitamin riboflavin. Like NAD+, this... 

Flavin adenine diphosphate (FAD, flavin adenine dinucleotide) and riboflavin 5 -monophosphate (FMN, flavin mononucleotide), whose structures are shown in Fig. 15-7, are perhaps the most versatile of all... 

Flavin adenine dinucleotide. See FAD Flavin adenine diphosphate. See FAD Flavin coenzymes 766,780 - 795 modified 788, 789 reduced 794 Flavin radicals 792 color of 794 formation constant 794 Flavocytochrome b2 782, 794, 847 Flavodoxins 793, 799, 800 Flavoprotein(s) 513, 788... 

The worst example is given by the flavin nucleotides FMN and FAD, the first of which is no nucleotide at all and the second no dinucleotide. The term FMN should simply be changed into FMP, viz. (ribo)flavin-monophosphate, while the abbreviation FAD might even be preserved as representing flavin-adenine-diphosphate . 

Riboflavin-5 -Adenosine Diphosphate. Riboflavin-5 -adenosine diphosphate [146-14-5] (flavin—adenine dinucleotide, FAD), C27H33N9O15P2 (2), mol wt 785.56, was first isolated in 1938 from the D-amino acid oxidase as its prosthetic group (95), where it was postulated to be... 

Figure 17-5. Oxidative decarboxylation of pyruvate by the pyruvate dehydrogenase complex. Lipoic acid is joined by an amide link to a lysine residue of the transacetylase component of the enzyme complex. It forms a long flexible arm, allowing the lipoic acid prosthetic group to rotate sequentially between the active sites of each of the enzymes of the complex. (NAD nicotinamide adenine dinucleotide FAD, flavin adenine dinucleotide TDP, thiamin diphosphate.)...

In nature, an enzyme requiring two co-factors, thiamine diphosphate 2 and flavin adenine dinucleotide, accomplishes the oxidation of pyruvate to acetyl phosphate. The thiazole ring in thiamine condenses at the 2-position with pyruvat eliminating carbon dioxide to give an activated species that is oxidised by the flavin. An enzymatic oxidation process then reactivates the reduced flavin. The redox... 

Fig. 1. Energy metabolism in the normal myocardium (ATP adenosine-5 -triphosphate, ADP adenosine-5 -diphosphate, P phosphate, PDH pyruvate dehydrogenase complex, acetyl-CoA acetyl-coenzyme A, NADH and NAD" nicotinamide adenine dinucleotide (reduced and oxidized), FADH2 and FAD flavin adenine dinucleotide (reduced and oxidized).

Fig. 2.1. Examples from The Energy Hall of Fame. These molecules not only deliver energy, but transfer special groups in the process. Acyl, RCO— ADP, adenosine diphosphate ATP, adenosine triphosphate dUMP deoxyuridine monophosphate FAD, flavin adenine dinucleotide GTP, guanosine triphosphate NADH, nicotinamide adenine dinucleotide NADP, nicotinamide adenine dinucleotide phosphate P, phosphate TMP, thymidine monophosphate UDP, uridine diphosphate UTP, uridine triphosphate.

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]. 

Note Abbreviations NADPH, [Lnicotinamide adenine dinucleotide phosphate reduced from NAD, [Lnicotinamide adenine dinucleotide FAD, flavin adenine dinucleotide PAPS, 3 -phosphoadenosine 5 -phosphosulfate UDPGA, uridine diphosphate-glucuronic acid. 

ADP AFP ab as ALAT AP ASAT ATP BQ BSA CEH CK CME COD con A CV d D E E EC ECME EDTA EIA /e FAD FET FIA G GOD G6P-DH HBg HCG adenosine diphosphate a-fetoprotein antibody antigen alanine aminotranferase alkaline phosphatase aspartate aminotransferase adenosine triphosphate benzoquinone bovine serum albumin cholesterol ester hydrolase creatine kinase chemically modified electrode cholesterol oxidase concanavalin A coefficient of variation (relative standard deviation) layer thickness diffusion coefficient enzyme potential Enzyme Classification enzyme-chemically modified electrode ethylene diamine tetraacetic acid enzyme immunoassay enzyme loading factor flavin adenine dinucleotide field effect transistor flow injection analysis amplification factor glucose oxidase glucose-6-phosphate dehydrogenase hepatitis B surface antigen human chorionic gonadotropin... 

MCD, magnetic circular dichroism EPR, electron paramagnetic resonance NMR, nuclear magnetic resonance DBM, Debye-Bohr magneton ADP, adenosine diphosphate ARN, adenosine-5 -nicotinate FAD, flavin-adenine dinucleotide... 

Figure 3 Schematic representation of the reactions cataiyzed by the acetoin dehydrogenase compiex. The Ei subunit (acetoin dehydrogenase) binds thiamine diphosphate (TDP) the E2 subunit (dihydroiipoyi transacetyiase) contains iipoamide the E3 subunit (dihydroiipoyi dehydrogenase) binds flavin adenine dinucieotide (FAD).

Abbreviations used NAD+ = nicotinamide adenine dinucleotide NADH e reduced nicotinamide adenine dinucleotide NADP = nicotinamide adenine dinudeotide phosphate NAD PH reduced nicotinamide adenine dinucleotide phosphate NMN, NMN+ nicotinamide mononucleotide NMNH2 = reduced nicotinamide mononucleotide a-NAD a-nicotinamide adenine dinucleotide AMP = 5 -adenylic acid 3,5 -AMP adenosine 3, 5 -cycIic phosphate 3 ,5 -UMP = uridine 3, 5 -cyclic phosphate 3, 5 -CMP cytidine 3, 5-cyclic phosphate 3 f5 GMP = guanosine 3 5f-cyclic phosphate 3, 5 TMP thymidine 3, 5 -cyclic phosphate Dibutyryl-3, 5 -AMP = N6,02-dibutyryladenosine 3, 5 -cyclic phosphate 2, 3 -UMP = uridine 2 ,3 -cyclic monophosphate 2, 3 -CMP cytidine 2, 3 -cyclic monophosphate 2, 3 -AMP = adenosine 2, 3 -cyclic monophosphate 2 ,3 -GMP = guanosine 2 3 -cyclic monophosphate 2 -UMP = uridine 2 -phosphate -UMP uridine -phosphate 5 -UMP = uridine 5 phosphate Poly U polyuridylic acid ADP = adenosine 5 -diphosphate FAD = flavin adenine dinucleotide UpA, UpU, ApU and ApA x dinucleoside phosphates of uridine and/or adenine. c See original references for experimental conditions and additional data. 

Another enzyme cofactor, flavine adenine dinucleotide (FAD) disodium salt, has been studied by 13C nmr. Assignments of the resonances have been made by comparing the spectrum of FAD with its constituents, adenosine 5 -diphosphate trisodium salt and riboflavin -monophosphate sodium salt (Breitmaier and Voelter, 1972). 

In riboflavin (7,8-dimethyl-10-(/ )-ribityl isoalloxazine), the polyol ribitol is connected via an amino bond to the chromophore. Riboflavin is not an iV-gly-coside. Accordingly, flavin mononucleotide (FMN, riboflavin S -phosphate) and flavin adenine dinucleotide (FAD riboflavin 5 -adenosine diphosphate) are hydrolyzable only in the nucleotide part (Scheme 7.2.22). 

The first committed step in the biosynthetic pathway of the branched chain amino acids is catalyzed by the enzyme acetohydroxyacid synthase (AHAS, EC 2.2.1.6), which is also referred to as acetolactate synthase (ALS). As depicted in Fig. 2.1.1, the pathway leading to valine and leucine begins with the condensation of two molecules of pyruvate accompanied by loss of carbon dioxide to give (S)-2-acetolactate. A parallel reaction leading to isoleucine involves the condensation of pyruvate with 2-ketobutyrate to afford (S)-2-aceto-2-hydroxybutyrate after loss of carbon dioxide. Both reactions are catalyzed by AHAS, which requires the cofactors thiamin diphosphate (ThDP) and flavin adenine dinudeotide (FAD). A divalent metal ion, most commonly is also required. Several excellent reviews... 

Adenosine diphosphate See Flavine adenine dinucleotide in The Combined Chemical Dictionary. 5 -a-D-Ribofuranoside Lampteroflavin [114590-52-2]... 

Other molecules that can accept two electrons are flavins FAD (flavin adenine dinucleotide) and FMN (flavin mononucleotide). The former coenzyme is formed by adenine-ribose-diphosphate, followed by a linear sugar-type molecule and, finally, the aromatic ring (isoalloxazine) of Figure 11.7. FMN is missing adenine, ribose, and one of the phosphates at the beginning of the chain. Flavins are prosthetic groups in fiavoproteins involved in the ET chain of Complex 11. 

The nucleotide coenzymes are structurally related to the mononucleotides. Typical nucleotide coenzymes are adenosine triphosphate (ATP), flavin-adenine-dinucleotide (FAD) and numerous other phosphate esters of complex structure, containing adenosine, guanosine, cytidine or uridine. Five coenzymes are known for example, which are derived from cytidine diphosphate (CDP) CDP-choline, CDP-ethanolamine, CDP-diglyceride, CDP-glycerol and CDP-ribitol. 

---