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NADH and NAD+

The leading substrate (A) is nicotinamide adenine dinucleotide (NAD ), and NAD and NADH (product Q) compete for a common site on E. A specific example is offered by alcohol dehydrogenase (ADH) ... [Pg.452]

The utility of the Zincke reaction has been extended to the preparation of various NAD and NADH analogs. Holy and co-workers synthesized a series of NAD analogs containing nucleotide bases as a means to study through-space interaction between the pyridinium and base portions. Nicotinamide-derived Zincke salt 8 was used to link with various adenine derivatives via tethers that contained hydroxyl (105 —> 106, Scheme 8.4.35), phosphonate (107—>108, Scheme 8.4.36), and carboxylate "... [Pg.370]

Looking at Figure 5.3 in isolation it would appear to be a satisfactory solution. However in practice it is not suffirient. Remember that there is only a finite amount of NAD+ and NADH in cells. Therefore the NADH has to be continually reoxidised to NAD+ making the latter available for continued operation of glycolysis. [Pg.130]

Reactions involve several enzymes, which have to follow in sequence for lactic acid and alcohol fermentation. This is known as the glucose catabolism pathway, with emphasis on energetic and energy carrier molecules such as ATP, ADP, NAD+ and NADH. In this pathway the six-carbon substrate yields two three-carbon intermediates, each of which passes through a sequence of reactions to the stable end product of pyruvic acid. [Pg.244]

Figure 7-9. Absorption spectra of NAD and NADH. Densities are for a 44 mg/L solution in a cell with a 1 cm light path. NADP and NADPH have spectrums analogous to NAD and NADH, respectively. Figure 7-9. Absorption spectra of NAD and NADH. Densities are for a 44 mg/L solution in a cell with a 1 cm light path. NADP and NADPH have spectrums analogous to NAD and NADH, respectively.
B. Nicotinamide and Flavin Coenzymes.—High-frequency (220 MHz) H n.m.r. spectroscopy shows that there are differences in conformation between oxidized and reduced pyridine coenzymes. A preliminary report on the P n.m.r. spectra of NAD+ and NADH confirms these observations, as the spectrum of NAD+ consists of an AB quartet while there is only a single resonance discernible in the spectrum of NADH. [Pg.135]

Both ADH and ALDH use NAD+ as cofactor in the oxidation of ethanol to acetaldehyde. The rate of alcohol metabolism is determined not only by the amount of ADH and ALDH2 enzyme in tissue and by their functional characteristics, but also by the concentrations of the cofactors NAD+ and NADH and of ethanol and acetaldehyde in the cellular compartments (i.e., cytosol and mitochondria). Environmental influences on elimination rate can occur through changes in the redox ratio of NAD+/NADH and through changes in hepatic blood flow. The equilib-... [Pg.419]

NADH, containing a tertiary amine functional group, has been readily determined by Ru(bpy)32+ ECL. However the oxidized form, NAD+, containing an aromatic secondary amine group produces virtually no ECL signal. This had led to a variety of indirect enzymic methods of analysis, where the activity of the enzyme results in the conversions between NAD+ and NADH. These are discussed in Sec. 8. [Pg.225]

Figure 10 Structures of NAD+ and NADH showing the part of the molecule where reversible reduction occurs, changing the ECL reactivity. Figure 10 Structures of NAD+ and NADH showing the part of the molecule where reversible reduction occurs, changing the ECL reactivity.
Figure 5. Ultraviolet spectrum of NAD+ and NADH. Note that the absorption band centered at 340 nm serves as a valuable way to assay many dehydrogenases as well as other enzymes that form products that can be coupled to NAD+ reduction or NADH oxidation. Figure 5. Ultraviolet spectrum of NAD+ and NADH. Note that the absorption band centered at 340 nm serves as a valuable way to assay many dehydrogenases as well as other enzymes that form products that can be coupled to NAD+ reduction or NADH oxidation.
Alberty analyzed the anion effect on pH-rate data. He first considered a one-substrate, one-product enzyme-catalyzed reaction in which all binding interactions were rapid equilibrium phenomena. He obtained rate expressions for effects on F ax and thereby demonstrating how an anion might alter a pH-rate profile. He also considered how anions may act as competitive inhibitors. The effect of anions on alcohol dehydrogenase has also been investigated. Chloride ions appear to affect the on- and off-rate constants for NAD and NADH binding. See also pH Studies Activation Optimum pH... [Pg.58]

The now classical example is lactate dehydrogenase. Sil-verstein and Boyer were the first to determine the rates of exchange between cognate pairs of reactants ie., lactate and pyruvate as well as NAD and NADH). Convenient [NADH]/[NAD ] and [pyruvate]/[lactate] ratios were chosen such that when combined they satisfied the apparent equilibrium constant for the LDH reaction. These investigators first established that each exchange rate was directly proportional to the duration of exchange and likewise directly proportional to enzyme concentration. As an additional control, they also demonstrated the equality of the pyruvate lactate exchange... [Pg.387]

Inhibitors of lactic dehydrogenase have been reported in commercial preparations of NAD+ and NADH (B4, M6, S28). The concentration of inhibitory substances varied from lot to lot. In a serum lactic dehydrogenase study with NAD+ from 8 sources, activities were found to vary from 145 to 75 units (B4). Inhibitors of lactic dehydrogenase activity have also been observed in dialyzates in uremic patients (W8) and in human urine (G8). The purity of available substrate can also effect enzyme activity. Schwartz and Bodansky observed that, in 6 batches of fructose 6-phosphate, all weighed to a 0.5 mM concentration, the actual concentration varied from 0.13 mAf to 0.55 mM (S14). [Pg.31]

This is the free-eneigy change for the oxidation-reduction reaction at pH 7, when acetaldehyde, ethanol, NAD+, and NADH are all present at 1.00 m concentrations. If, instead, acetaldehyde and NADH were present at 1.00 Mbut ethanol and NAD+ were present at 0.100 m, the value for AG would be calculated as follows. First,... [Pg.511]

Dependence of Electromotive Force on Concentrations Calculate the electromotive force (in volts) registered by an electrode immersed in a solution containing the following mixtures of NAD+ and NADH at pH 7.0 and 25 °C, with reference to a half-cell of E ° 0.00 V... [Pg.520]

Redox pairs Oxidation (loss of electrons) of one compound is always accompanied by reduction (gain of electrons) of a second substance. For example, Figure 6.11 shows the oxidation of NADH to NAD+ accompanied by the reduction of FAD to FADH2. Such oxidation-reduction reactions can be written as the sum of two halfreactions an isolated oxidation reaction and a separate reduction reaction (see Figure 6.11). NAD+ and NADH form a redox pair, as do FAD and FADH2. Redox pairs differ in their tendency to lose electrons. This tendency is a characteristic of a particular redox pair, and can be quantitatively specified by a constant, E (the standard reduction potential), with units in volts. [Pg.76]

Figure 15-2 Absorption spectra of NAD+ and NADH. Spectra of NADP+ and NADPH are nearly the same as these. The difference in absorbance between oxidized and reduced forms at 340 nm is the basis for what is probably the single most often used spectral measurement in biochemistry. Reduction of NAD+ or NADP+ or oxidation of NADH or NADPH is measured by changes in absorbance at 340 nm in many methods of enzyme assay. If a pyridine nucleotide is not a reactant for the enzyme being studied, a coupled assay is often possible. For example, the rate of enzymatic formation of ATP in a process can be measured by adding to the reaction mixture the following enzymes and substrates hexokinase + glucose + glucose-6-phosphate dehydrogenase + NADP+. As ATP is formed, it phosphorylates glucose via the action of hexokinase. NADP+ then oxidizes the glucose 6-phosphate that is formed with production of NADPH, whose rate of appearance is monitored at 340 nm. Figure 15-2 Absorption spectra of NAD+ and NADH. Spectra of NADP+ and NADPH are nearly the same as these. The difference in absorbance between oxidized and reduced forms at 340 nm is the basis for what is probably the single most often used spectral measurement in biochemistry. Reduction of NAD+ or NADP+ or oxidation of NADH or NADPH is measured by changes in absorbance at 340 nm in many methods of enzyme assay. If a pyridine nucleotide is not a reactant for the enzyme being studied, a coupled assay is often possible. For example, the rate of enzymatic formation of ATP in a process can be measured by adding to the reaction mixture the following enzymes and substrates hexokinase + glucose + glucose-6-phosphate dehydrogenase + NADP+. As ATP is formed, it phosphorylates glucose via the action of hexokinase. NADP+ then oxidizes the glucose 6-phosphate that is formed with production of NADPH, whose rate of appearance is monitored at 340 nm.
The nearby His 110, Asp 43, and Lys 77 may also participate in catalysis.76 77 The kinetics are unusual. Both NAD+ and NADH are bound tightly and the overall rate of reduction of a substrate is limited by the rate of dissociation of NADL78 Citrate is a natural uncompetitive inhibitor of aldose reductase.79... [Pg.774]

Calculated from the lactate/pyruvate ratio, assuming NAD and NADH at equilibrium, and using an equilibrium constant of 1.11 X 10-4. [From R. L. Veech, L. V. Eggleston, and H. A. Krebs, Biochem. 7.115, 609(1969).]... [Pg.521]

Exercise 9-20 A solution containing the two forms of the important coenzyme nicotinamide adenine dinuclaotide (abbreviated, NAD and NADH see Section 15-6C for structures) has an absorbance in a 1-cm cell of 0.311 at 340 nm and 1.2 at 260 nm. Both NAD and NADH absorb at 260 nm, but only NADH absorbs at 340 nm. The molar extinction coefficients are... [Pg.294]

One photoprocess reduces nicotinamide adenine dinucleotide phosphate (NADP ) to NADPH. These dinucleotides, shown below, differ from NAD and NADH (Section 15-6C) in having a phosphate group at C2 of one of the ribose units. The oxidized form, NADP , behaves like NAD and receives the equivalent of H e at C4 of the nicotinamide ring to form NADPH ... [Pg.940]

NADH is highly fluorescent, with absorption and emission maxima located at 340 and 450 nm, respectively, while NAD+ and NADH+ are not fluorescent (Figures 7.14 and 7.15). Schauenstein et al. (1980) explained the spectral modification of NADH+ by a higher percentage of the stacked conformation at a lower pH. [Pg.108]


See other pages where NADH and NAD+ is mentioned: [Pg.665]    [Pg.287]    [Pg.135]    [Pg.56]    [Pg.219]    [Pg.544]    [Pg.102]    [Pg.388]    [Pg.36]    [Pg.153]    [Pg.513]    [Pg.467]    [Pg.1017]    [Pg.1018]    [Pg.154]    [Pg.294]    [Pg.154]    [Pg.292]    [Pg.350]    [Pg.458]    [Pg.79]    [Pg.115]    [Pg.412]    [Pg.464]    [Pg.63]   
See also in sourсe #XX -- [ Pg.2 ]




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