Nicotinamide adenine dinucleotide reduction with

Nicotinamide, (S)-N-(a-methylbenzyl)-hydrogen bonding, 2, 111 Nicotinamide, N-phenyl-hydrogen bonding, 2, 111 Nicotinamide adenine dinucleotide in biochemical pathways, 1, 248 coenzyme system with NADH, 2, 121 reactions, 2, 382 reduction, 2, 281, 283... 

The first step in the biological degradation of lysine is reductive animation with a-ketoglutarate to give saccharopine. Nicotinamide adenine dinucleotide phosphate (NADPH), a relative of NADH, is the reducing agent. Show the mechanism. 

Newman, Melvin S., 93 Newman projection, 93 molecular model of, 93 Nicotinamide adenine dinucleotide, biological oxidations with, 625-626 reactions of, 725 structure of, 725, 1044 Nicotinamide adenine dinucleotide (reduced), biological reductions with, 610-611... 

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. 

Figure 18.2 Summary of respiratory energy flows. Foods ate converted into the reduced form of nicotinamide adenine dinucleotide (NADH), a strong reductant, which is the most reducing of the respiratory electron carriers (donors). Respiration can he based on a variety of terminal oxidants, such as O2, nitrate, or fumarate. Of those, O2 is the strongest, so that aerobic respiration extracts the largest amount of free energy from a given amount of food. In aerobic respiration, NADH is not oxidized directly by O2 rather, the reaction proceeds through intermediate electron carriers, such as the quinone/quinol couple and cytochrome c. The most efficient respiratory pathway is based on oxidation of ferrocytochrome c (Fe ) with O2 catalyzed by cytochrome c oxidase (CcO). Of the 550 mV difference between the standard potentials of c)Tochrome c and O2, CcO converts 450 mV into proton-motive force (see the text for further details).

The most important product of the hexose monophosphate pathway is reduced nicotinamide-adenine dinucleotide phosphate (NADPH). Another important function of this pathway is to provide ribose for nucleic acid synthesis. In the red blood cell, NADPH is a major reducing agent and serves as a cofactor in the reduction of oxidized glutathione, thereby protecting the cell against oxidative attack. In the syndromes associated with dysfunction of the hexose monophosphate pathway and glutathione metabolism and synthesis, oxidative denaturation of hemoglobin is the major contributor to the hemolytic process. 

It is helpful to think of the photosynthesis reaction as the sum of an oxidation half reaction and a reduction half reaction as shown in Figure 1. In fact, nature does separate these half reactions, in that the reduction of C02 to carbohydrates occurs in the stroma of the chloroplast, the organelle in the leaf where the photosynthesis reaction occurs, - whereas, the light-driven oxidation half reaction takes place on the thylakoid membranes which make up the grana stacks within the chloroplast. Reduced nicotinamide adenine dinucleotide phosphate (NADPH) carries the reducing power and most of the energy to the stroma to drive the fixation of C02 with the help of some additional energy provided... 

As a consequence of the previous considerations Kieber et al. [75] have developed an enzymic method to quantify formic acid in non-saline water samples at sub-micromolar concentrations. The method is based on the oxidation of formate by formate dehydrogenase with corresponding reduction of /3-nicotinamide adenine dinucleotide (j6-NAD+) to reduced -NAD+(/3-NADH) jS-NADH is quantified by reversed-phase high performance liquid chromatography with fluorimetric detection. An important feature of this method is that the enzymic reaction occurs directly in aqueous media, even seawater, and does not require sample pre-treatment other than simple filtration. The reaction proceeds at room temperature at a slightly alkaline pH (7.5-8.5), and is specific for formate with a detection limit of 0.5 im (SIN = 4) for a 200 xl injection. The precision of the method was 4.6% relative standard deviation (n = 6) for a 0.6 xM standard addition of formate to Sargasso seawater. Average re-... 

Most asymmetric reductions that can be enzymatically effected have been the reactions of ketones. These reactions can be conducted with whole cells as well as with isolated enzymes. In the latter case, of course, at least one equivalent of a cofactor such as NADH or NADPH (nicotinamide adenine dinucleotide) is required to serve as the actual reductant in the reaction system. 

Gibb, W., Jeffery, J. The steric course with respect to the reduced nicotinamide-adenine dinucleotide of the reduction of 3-oxo steroids catalyzed by cortisone reductase. European J. Biochem. 34, 395—400 (1973). 

The nicotinamide coenzymes nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate (NADPH) are associated with a wide variety of enzymes involved in oxidation-reduction reactions (Fig. 21). NADH is typically involved in oxidative catabolic reactions, while NADPH is primarily used in biosynthetic pathways [58]. 

NAD is one of Nature s most important oxidizing agents it can be considered as a biological equivalent of the chromium(VI) ion. NAD is shorthand for nicotinamide adenine dinucleotide it is a co-enzyme, which together with an enzyme is essential for several life-sustaining processes (Box 2.2). On reduction it forms the corresponding 1,4-dihydropyridine, NADH, The oxidation of ethanol to acetaldehyde (ethanal) is effected by the enzyme alcohol dehydrogenase and mediated by NAD (Scheme 2.31). 

The reduction of 5-nitrouracil derivatives 381 has been performed using l-benzyl-l,4-dihydronicotinamide 382 as a reduced nicotinamide adenine dinucleotide (NADH) model <1998H(49)475>, although the same products can also be obtained with sodium borohydride <1976JME1072>. 

Two vitamins, nicotinamide and pyridoxine (vitamin B6), are pyridine derivatives. Nicotinamide participates in two coenzymes, coenzyme I (65 R = H) which is known variously as nicotinamide adenine dinucleotide (NAD) or diphosphopyridine nucleotide (DPN), and coenzyme II (65 R = P03H2) also called triphosphopyridine nucleotide (TPN) or nicotinamide adenine dinucleotide phosphate (NADP). These are involved in many oxidation-reduction processes, the quaternized pyridine system acting as a hydrogen acceptor and hydrogen donor. Deficiency of nicotinamide causes pellagra, a disease associated with an inadequately supplemented maize diet. Nicotinic acid (niacin) and its amide are... 

Functioning of the enzyme requires the presence of a coenzyme, nicotinamide adenine dinucleotide which exists in its oxidized (NAD+) or reduced (NADH) forms. The structure of NADH is shown in (177). Reduction or oxidation occurs by transfer of the pro-R C-4 hydrogen atom of the nicotinamide stereospecifically to or from the substrate. The reaction is therefore a ternary one, with the substrate and coenzyme necessarily within the active site for the reaction to occur.l46Sa... 

Nicotinamide adenine dinucleotide phosphate (NADPFI) A biochemical cofactor (a nonprotein chemical that can interact with an enzyme) that can donate electrons for the reduction of molecules. 

We shall start the discussion with a classical experiment related to the stereochemistry of oxidation of ethanol and reduction of acetaldehyde mediated by the enzyme yeast alcohol dehydrogenase in the presence of the oxidized (NAD+) and reduced (NADH) forms, respectively, of the coenzyme nicotinamide adenine dinucleotide (Fig. 54). The stereochemically interesting feature of this reaction stems from the fact that the methylene hydrogens in CH3CH2OH and the faces of the carbonyl in CH3CH = 0 are enantiotopic. The question thus arises which of the CH2-hydrogens... 

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