Nicotinamide adenine dinucleotide phosphates NADP/NADPH

Nicotinamide Adenine Dinucleotide Phosphate (NADP/NADPH)... 

Today s systems are in most cases based on the bioluminescence with ATP and luciferase from the firefly. As an alternative system it is also possible to use a colour test nicotinamide adenine dinucleotides (NAD/NADH) and nicotinamide adenine dinucleotide phosphates (NADP/NADPH), which are also compounds used for the energy transfer in the metabolism in living cells or compounds found in food debris. 

Indicators There are certain compounds that are suitable as indicators for sensitive and specific clinical analysis. Nicotinamide adenine dinucleotide (NAD) occurs in oxidized (NAD" ) and reduced (NADH) forms. Nicotinamide adenine dinucleotide phosphate (NADP) also has two states, NADP" and NADPH. NADH has a very high uv—vis absorption at 339 nm, extinction coefficient = 6300 (M cm) , but NAD" does not. Similarly, NADPH absorbs light very strongly whereas NADP" does not. 

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... 

FMN was first identified as the coenzyme of an enzyme system that catalyzes the oxidation of the reduced nicotinamide coenzyme, NADPH (reduced NADP), to NADP (nicotinamide adenine dinucleotide phosphate). NADP is an essential coenzyme for glucose-6-phosphate dehydrogenase which catalyzes the oxidation of glucose-6-phosphate to 6-phosphogluconrc acid. This reaction initiates the metabolism of glucose by a pathway other than the TCA cycle (citric acid cycle). The alternative route is known as the phosphoglneonate oxidative pathway, or the hexose monophosphate shunt. The first step is ... 

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 ... 

An important aspect of enzymatic oxidation-reduction reactions involves the transfer of hydrogen atoms. This transfer is mediated by coenzymes (substances that act together with enzymes) nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). These two species pick up H atoms to produce NADH and NADPH, respectively, both of which can function as hydrogen atom donors. Another pair of species involved in oxidation-reduction processes by hydrogen atom transfer consists of flavin adenine triphosphate (FAD) and its hydrogenated form FADH2. The structural formulas of NAD and its cationic form, NAD+, are shown in Figure 4.7. 

There are two other cofactors that can participate in redox processes these are /lavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide phosphate (NADP+). both of which are shown in Fig. 11-2. FAD accepts 2H s and is thereby reduced to FADH2, whereas NADP+ accepts H and is reduced to NADPH and H +. Both of these reduced cofactors can be oxidized, thereby donating their H s (or reducing equivalents), similar to the oxidation of NADH. The enzymes that catalyze those reactions involving an oxidation or a reduction are usually very selective toward a particular cofactor (NAD or NADP) in a particular oxidation state. 

Figure 5-1. Schematic representation of the three stages of photosynthesis in chloroplasts (1) The absorption of light can excite photosynthetic pigments, leading to the photochemical events in which electrons are donated by special chlorophylls. (2) The elections are then transferred along a series of molecules, causing the oxidized form of nicotinamide adenine dinucleotide phosphate (NADP+) to become the reduced form (NADPH) ATP formation is coupled to the electron transfer steps. (3) The biochemistry of photosynthesis can proceed in the dark and requires 3 mol of ATP and 2 mol of NADPH per mole of C02 fixed into a carbohydrate, represented in the figure by (CH20).

Photosynthesis comprises a light-induced and a dark reaction. The first, called photophosphorylation, involves the two-electron reduction of nicotinamide adenine dinucleotide phosphate (NADP+) by water, to produce NADPH and oxygen. The redox reaction is coupled to the generation of adenosine triphosphate (ATP) from adenosine diphosphate (ADP) ... 

The pentose phosphate pathway (PPP) is the major pathway for recycling nicotinamide adenine dinucleotide (NAD) to nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) and for the production of ribose-5-phosphate that is needed for the synthesis of nucleotides. The function of the PPP depends on the synthesis of nicotinamide-adenine dinucleotide phosphate (NADP) and thiamin pyrophosphate, a coenzyme... 

Nicotinamide adenine dinucleotide (NAD and its reduced form dihydronicotinamide adenine dinucleotide (NADH)) as well as nicotinamide adenine dinucleotide phosphate (NADP and its reduced form nicotinamide adenine dinucleotide phosphate hydrogen (NADPH)) are essential co-factors for many dehydrogenases. The presence of NAD was first demonstrated in P. gallinaceum (Speck and Evans, 1945) and later studies showed increased levels of these pyridine nucleotides in P. lophurae, P. berghei and P. falciparum. Trager (1977) reported that high levels of... 

The electron donor in most reductive biosyntheses is NADPH, the reduced form of nicotinamide adenine dinucleotide phosphate (NADP see Figure 14.13). NADPH differs from NADH in that the 2 -hydroxyl group of its adenosine moiety is esterified with phosphate. NADPH carries electrons in the same way as NADH. However, NADPH is used almost exclusively for reductive biosyntheses, whereas NADH is used primarily for the generation of ATP. The extra phosphoryl group on NADPH is a tag that enables enzymes to distinguish between high-potential electrons to be used in anabolism and those to be used in catabolism. 

The operation of tandem cells bears a close similarity to the processes that take place in photosynthesis where there are also two photosystems connected in series. In the first, light is absorbed by chlorophyll and this acts as a mediator to oxidize water to oxygen [reaction (4.21)], while in the second, the organic compound nicotinamide adenine dinucleotide phosphate (NADP) is reduced by electrons to a state generally designated NADPH. 

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