Nicotinamide adenine dinucleotide hydride NADH

Growth of mammary breast cancer cells, which also express the same NIS as thyroid cells, is inhibited by iodine and also 6-iodolactone. Thus, a sufficient iodine supply has an important role, not only for thyroid function and growth, but also for the mammary gland. 2-IHDA, inhibits nicotinamide adenine dinucleotide hydride (NADH)-dependent H2O2 generation in vitro, as well as in vivo. It also inhibits adenylate-cyclase activity, and therefore is supposed to mediate the well-known Wolff—Chaikoff effect. 

Nicotinamide adenine dinucleotide hydride (NADH) Metabolite that can carry electron pairs to different places in the cell. These pairs can be used for building chemical bonds or burning (respiration for energy by combination with oxygen). Most cells also use a second functionally identical form with an added phosphate called NADPH. 

To obtain in vitro activity for PrnA, nicotinamide adenine dinucleotide-hydride (NADH) was required as a co-factor, and during the purification process, it was found that both FAD and a flavin reductase were also required to maintain chlorinase activity. In vitro, specific flavin reductases were not required, and flavin reductases firom a number of bacteria have been used successfully in in vitro experiments. NADH, in combination with the flavin reductase, reduces FAD to the... 

Rhodium and ruthenium complexes have also been studied as effective catalysts. Rh(diphos)2Cl [diphos = l,2-bis(diphenyl-phosphino)ethane] catalyzed the electroreduction of C02 in acetonitrile solution.146 Formate was produced at current efficiencies of ca. 20-40% in dry acetonitrile at ca. -1.5 V (versus Ag wire). It was suggested that acetonitrile itself was the source of the hydrogen atom and that formation of the hydride HRh(diphos)2 as an active intermediate was involved. Rh(bpy)3Cl3, which had been used as a catalyst for the two-electron reduction of NAD+ (nicotinamide adenine dinucleotide) to NADH by Wienkamp and Steckhan,147 has also acted as a catalyst for C02 reduction in aqueous solutions (0.1 M TEAP) at -1.1 V versus SCE using Hg, Pb, In, graphite, and n-Ti02 electrodes.148 Formate was the main... 

Hydride transfer is one of the fundamental chemical and biological reactions. The mechanism of the formal hydride transfer from the nicotinamide adenine dinucleotide coenzyme (NADH) and its analogues to the surrounding... 

Nicotinamide is an essential part of two important coenzymes nicotinamide adenine dinucleotide (NAD ) and nicotinamide adenine dinucleotide phosphate (NADP ) (Figure 18.19). The reduced forms of these coenzymes are NADH and NADPH. The nieotinamide eoenzymes (also known as pyridine nucleotides) are electron carriers. They play vital roles in a variety of enzyme-catalyzed oxidation-reduction reactions. (NAD is an electron acceptor in oxidative (catabolic) pathways and NADPH is an electron donor in reductive (biosynthetic) pathways.) These reactions involve direct transfer of hydride anion either to NAD(P) or from NAD(P)H. The enzymes that facilitate such... 

Reduced nicotinamide-adenine dinucleotide (NADH) plays a vital role in the reduction of oxygen in the respiratory chain [139]. The biological activity of NADH and oxidized nicotinamideadenine dinucleotide (NAD ) is based on the ability of the nicotinamide group to undergo reversible oxidation-reduction reactions, where a hydride equivalent transfers between a pyridine nucleus in the coenzymes and a substrate (Scheme 29a). The prototype of the reaction is formulated by a simple process where a hydride equivalent transfers from an allylic position to an unsaturated bond (Scheme 29b). No bonds form between the n bonds where electrons delocalize or where the frontier orbitals localize. The simplified formula can be compared with the ene reaction of propene (Scheme 29c), where a bond forms between the n bonds. 

Zinc-containing alcohol dehydrogenases take up two electrons and a proton from alcohols in the form of a hydride. The hydride acceptor is usually NAD(P) (the oxidized form of nicotinamide adenine dinucleotide (NADH) or its phosphorylated derivative, NADPH). Several liver alcohol dehydrogenases have been structurally characterized, and Pig. 17.8 shows the environment around the catalytic Zn center and the bound NADH cofactor. 

GABA HMG-CoA HMPA HT LDA LHMDS LTMP NADH NBH NBS NCS NIS NK NMP PMB PPA RaNi Red-Al RNA SEM SnAt TBAF TBDMS TBS Tf TFA TFP THF TIPS TMEDA TMG TMP TMS Tol-BINAP TTF y-aminobutyric acid hydroxymethylglutaryl coenzyme A hexamethylphosphoric triamide hydroxytryptamine (serotonin) lithium diisopropylamide lithium hexamethyldisilazane lithium 2,2,6,6-tetramethylpiperidine reduced nicotinamide adenine dinucleotide l,3-dibromo-5,5-dimethylhydantoin A-bromosuccinimide A-chlorosuccinimide A-iodosuccinimide neurokinin 1 -methyl-2-pyrrolidinone para-methoxybenzyl polyphosphoric acid Raney Nickel sodium bis(2-methoxyethoxy)aluminum hydride ribonucleic acid 2-(trimethylsilyl)ethoxymethyl nucleophilic substitution on an aromatic ring tetrabutylammonium fluoride tert-butyldimcthyisilyl fert-butyldimethylsilyl trifluoromethanesulfonyl (triflyl) trifluoroacetic acid tri-o-furylphosphine tetrahydrofuran triisopropylsilyl A, N,N ,N -tetramethy lethylenediamine tetramethyl guanidine tetramethylpiperidine trimethylsilyl 2,2 -bis(di-p-tolylphosphino)-l,r-binaphthyl tetrathiafulvalene... 

Isotope effects have been used to determine whether the hydride transfer from the enzyme cofactor nicotinamide-adenine dinucleotide (NADH) (reaction (43)) takes place as a hydride ion transfer in a single kinetic step or in a multistep reaction via an uncoupled electron and hydrogen transfer. 

In the second stage, the building blocks are degraded by various pathways in tissues to a common metabolic intermediate, acetyl CoA. Most of the energy contained in metabolic fuels is conserved in the chemical bonds (electrons) of acetyl CoA. A smaller portion is conserved in reducing nicotinamide adenine dinucleotide (NAD) to NADH or flavin adenine dinucleotide (FAD) to FADH. Reduction indicates the addition of electrons that may be free, part of a hydrogen atom (H), or a hydride ion (H ). 

In marked contrast, nature s reducing agent, reduced nicotinamide adenine dinucleotide (NADH), delivers hydride in a stereospecific manner because it is a cofactor in an enzyme-catalysed reaction. For example, reduction of pyruvic acid to lactic acid in vertebrate muscle occurs via attack of hydride to produce just one enantiomer, namely (5)-lactic acid. 

NADH (reduced nicotinamide adenine dinucleotide) is utilized in biological reductions to deliver hydride to an aldehyde or ketone carbonyl group (see Box 7.6). A proton from water is used to complete the process, and the product is thus an alcohol. The reaction is catalysed by an enzyme called a dehydrogenase. The reverse reaction may also be catalysed by the enzyme, namely the oxidation of an alcohol to an aldehyde or ketone. It is this reverse reaction that provides the dehydrogenase nomenclature. 

During the reduction sequence, NADH transfers a hydride from a prochiral centre on the dihydropyridine ring, and is itself oxidized to NAD+ (nicotinamide adenine dinucleotide) that contains a planar pyridinium ring. In the oxidation sequence, NAD+ is reduced to NADH by acquiring hydride to an enantiotopic face of the planar ring. The reactions are completely stereospecific. 

FIGURE 13-15 NAD and NADR (a) Nicotinamide adenine dinucleotide, NAD +, and its phosphorylated analog NADP+ undergo reduction to NADH and NADPH, accepting a hydride ion (two electrons and one proton) from an oxidizable substrate. The hydride ion is added to either the front (the A side) or the back (the B side) of the planar nicotinamide ring (seeTable 13-8). (b)The UV absorption spec-... 

Nickel-cadmium cell Ni-Cd cell Nickel-iron rechargeable cell -> Edison cell Nickel-metal hydride cell - Ni-MFlcell Nicotinamide adenine dinucleotide - NADH Nigraniline - poly aniline... 

The nicotinamide ring of nicotinamide adenine dinucleotide can exist in both oxidized (NAD+) and reduced (NADH) forms, where the reduced form can be viewed as a double vinylogous amine, i.e. a double enamine. The hydrogen transfer from the C4 atom is widely believed to proceed by a hydride transfer mechanism, reminiscent of the mechanism of carbonyl reduction by metal hydrides. 

The oxidizing agent is a compound that, like ATP, constantly appears in these reactions nicotinamide adenine dinucleotide (NAD). The functional group here, we remember (Sec. 36.15), is the pyridine ring, which can accept a hydride ion to form NADH. Like the hemiacetal moiety, NAD is bound to the enzyme, and in a position for easy reaction (Fig. 37.3). 

NADH (nicotinamide adenine dinucleotide) is a biochemical source of hydride. In the following example NADH reduces acetaldehyde to ethanol via minor pathway H t., hydride transfer to a cationic center. A Zn ion acts as a Lewis acid to polarize the acetaldehyde carbonyl (similar to protonating the carbonyl). The Lewis acid makes the carbonyl a better electron sink by increasing the partial positive charge on carbon. In fact, the electrophilic catalysis by 2+ and 3+ metal ions can accelerate additions to carbonyls by over a million times. The formation of the aromatic pyridinium ring in the NAD" product helps balance the energetics of this easily reversible reaction. 

Since many of the transformations undergone by metabolites involve changes in oxidation state, it is understandable that cofactors have been developed to act as electron acceptors/donors. Two of the most important are NAD and NADP (Figure 5.2). Nicotinamide adenine dinucleotide (NAD ) can accept what is essentially two electrons and a proton (a hydride ion) from a substrate like ethanol in a reaction catalysed by alcohol dehydrogenase, to give the oxidised product, acetaldehyde, and the reduced cofactor NADH plus a proton ... 

Fig. 1.5 Nicotinamide adenine dinucleotide (NAD+) and its phosphorylated analog (NADP+). The difference is indicated in purple. NAD+ and NADP+ undergo reduction to NADH and NADPH by accepting a hydride ion and two electrons and releasing a proton from an oxidized substrate. (Adapted from Fig. 14-13 in Berg JM, Tymoczko JL and Stryer L. Biochemistry, 5th Ed. 2002. W.H. Freeman Co., New York)...

Chemical energy in the form of reduced NAD+, NADH. Nicotinamide adenine dinucleotide (NAD+) is a coenz)rme derived from the vitamin niacin. The reduced form of NAD+, NADH, carries hydride anions, hydrogen atoms with two electrons (H ), removed during the oxidation of one of the substrates, glyceraldehyde-3-phosphate (see Figure 21.7, step 6). Under aerobic conditions the electrons and hydrogen atom are transported... 

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