Nicotinamide - adenine dinucleotide

Nicotinamide adenine dinucleotide (NAD) and its derivative nicotinamide adenine dinucleotide phosphate (NADP) are cofactors and redox-active components essential for life in all organisms. They also play a vital and rate-limiting role in the generation and scavenging of reactive oxygen species (ROS) [13-15] 

NAD biosynthesis is commonly divided into the de novo and the salvage pathways. In many plants and bacteria, the de novo biosynthesis starts with aspartate or tryptophan to give quinolinic acid [16, 17]. 

NaMN is biosynthesized either from quinolinic acid via the de novo pathway or from degradation products via the salvage pathway. 

The N1C2 gene encodes nicotinamidase, which acts in recycling nicotinamide back to NAD [24], 

Plants produce various pyridine alkaloids derived from nicotinic acid. Trigonelline, the major component in coffee seeds, and ricinine, the toxic alkaloid produced by Ricinus communis, are formed from nicotinic acid originating from the NAD catabolism [20, 25, 26], Quinolinic acid was found to be an efficient precursor in the biosynthesis of nicotine [27]. 

At more or less the same time, the chemistry of an important class of enzymic oxidation-reduction reactions was partially elucidated by a group of investi- 

By using dideuterioethanol, CH3CD2OH, as substrate, they demonstrated that one atom of deuterium is transferred from substrate to coenzyme, and further that this atom of deuterium is transferred from the coenzyme, under the influence of lactic dehydrogenase, to pyruvate (Fisher, et al., 1953 Loewus et al., 1953a,b Vennesland and Westheimer, 1954). The converse experiment was also carried out, that is to say, the reactions were performed with normal substrate and coenzyme, but in D20 this resulted in transfer of ordinary hydrogen from substrate to coenzyme. The question they had set out to answer was then settled the oxidation-reductions proceed by direct transfer of hydrogen between substrate and coenzyme. These results have subsequently been confirmed in numerous investigations with other enzymic reactions that require NAD+ or NADP+. 

But the results provided an exciting bonus. The reactions proved to be stereospecific. NAD+ that has been reduced with dideuterioethanol has both a hydrogen atom and a deuterium atom in the 4-position of the pyridine ring, but reductions of pyruvate or of acetaldehyde with NAD(D) prepared enzymically in this way quantitatively transfer deuterium, and leave the hydrogen atom in place. The 1954 diagram showing the stereospecific transfer of hydrogen from the 4-position of NADH is presented in (5). 

Transhydrogenases (e. g. lactate dehydrogenase, alcohol dehydrogenase) dehydrogenate or hydro- 

The oxidized and reduced forms of the pyridine cosubstrate are readily distinguished by absorbance readings at 340 nm (Fig. 2.5). Therefore, whenever possible, enzymatic reactions which are difficult to measure directly are coupled with an NAD(P)-dependent indicator reaction (cf. 2.6.1.1) for food analysis. 

Until the absolute configuration of the chiral center is determined, the two sides of the pyridine ring are denoted as A and B. 

5 Acting on C—N bonds, other than peptide bonds  

This has been established by replacing either the pro-S or the pro-R hydrogen by deuterium and seeing whether the deuterium is retained by acetaldehyde or is taken up by NADH. 

NAD is used in metabolism or catabolism, for example, turning sugars into energy, NADP is used for anabolism or building up chemicals. Nature, in this way, keeps the two kinds of process separated. 

---

FIGURE 15 5 Structure of NAD the oxidized form of the coenzyme nicotinamide adenine dinucleotide The functional part of the coen zyme is framed in red... 

NADH is the reduced form of nicotinamide adenine dinucleotide. 

Insects poisoned with rotenone exhibit a steady decline ia oxygen consumption and the iasecticide has been shown to have a specific action ia interfering with the electron transport iavolved ia the oxidation of reduced nicotinamide adenine dinucleotide (NADH) to nicotinamide adenine dinucleotide (NAD) by cytochrome b. Poisoning, therefore, inhibits the mitochondrial oxidation of Krebs-cycle iatermediates which is catalysed by NAD. 

Glucose [50-99-7] urea [57-13-6] (qv), and cholesterol [57-88-5] (see Steroids) are the substrates most frequentiy measured, although there are many more substrates or metaboUtes that are determined in clinical laboratories using enzymes. Co-enzymes such as adenosine triphosphate [56-65-5] (ATP) and nicotinamide adenine dinucleotide [53-84-9] in its oxidized (NAD" ) or reduced (NADH) [58-68-4] form can be considered substrates. Enzymatic analysis is covered in detail elsewhere (9). 

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. 

Fig. 9. Glucuionic acid pathway. NAD = nicotinamide-adenine dinucleotide NADH = reduced nicotinamide—adenine dinucleotide ...

NADP = nicotinamide-adenine dinucleotide phosphate NADPH = reduced nicotinamide—adenine dinucleotide phosphate NDP = nucleoside... 

The result of this biosynthesis is that the product is nicotinic acid mononucleotide rather than free nicotinic acid. Ingested nicotinic acid is converted to nicotinic acid mononucleotide which, in turn, is converted to nicotinic acid adenine dinucleotide. Nicotinic acid adenine dinucleotide is then converted to nicotinamide adenine dinucleotide. If excess nicotinic acid is ingested, it is metabolized into a series of detoxification products (Fig. 4). Physiological metabohtes include /V-methylnicotinamide (19) and A/-methyl-6-pyridone-2-carboxamide (24) (1). 

Coenzymes such as adenosine diphosphate (ADP), adenosine SGtriphosphate (ATP), nicotinamide adenine dinucleotide (NAD), and nicotinamide adenine dinucleotide, reduced (NADH), are involved in some reactions (4). 

NAD" — see Nicotinamide adenine dinucleotide NADP" — see Nicotinamide adenine dinucleotide phosphate NADPH... 

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... 

In oiological systems, the most frequent mechanism of oxidation is the remov of hydrogen, and conversely, the addition of hydrogen is the common method of reduc tion. Nicotinamide-adenine dinucleotide (NAD) and nicotinamide-adenine dinucleotide phosphate (NADP) are two coenzymes that assist in oxidation and reduction. These cofactors can shuttle between biochemical reac tions so that one drives another, or their oxidation can be coupled to the formation of ATP. However, stepwise release or consumption of energy requires driving forces and losses at each step such that overall efficiency suffers. 

Biological activity (BA) was chosen as such parameter. The BA determined using a system and a technique for a class of natural polyphenolic bonds nicotinamide adenine dinucleotide restored (NAD H ) - ferricyanide (KjFe(CN)g) in a phosphates buffer solution. 

Oxidation of P-nicotinamide adenine dinucleotide (NADH) to NAD+ has attracted much interest from the viewpoint of its role in biosensors reactions. It has been reported that several quinone derivatives and polymerized redox dyes, such as phenoxazine and phenothiazine derivatives, possess catalytic activities for the oxidation of NADH and have been used for dehydrogenase biosensors development [1, 2]. Flavins (contain in chemical structure isoalloxazine ring) are the prosthetic groups responsible for NAD+/NADH conversion in the active sites of some dehydrogenase enzymes. Upon the electropolymerization of flavin derivatives, the effective catalysts of NAD+/NADH regeneration, which mimic the NADH-dehydrogenase activity, would be synthesized [3]. 

P-Nicotinamide adenine dinucleotide reduced di-Na salt trihydrate (reduced diphosphopyridine nucleotide sodium salt, NADH) [606-68-8] M 763.5, pK as for NAD. 

Nicotinamide adenine dinucleotide phosphate (NADP, TPN) [53-59-8] M 743.4, pK] 1.1 (PO4H2), pK 4.0 (adenine NH ), pKa 6.1 (P04 ). Purified by anion-exchange chromatography in much the same way as for NAD [Dalziel and Dickinson Biochem J 95 311 7965 Biochemical Preparations 11 87 7966]. Finally it is purified by dissolving in H2O and precipitating with 4 volumes of Me2CO and dried in... 

Nicotinamide adenine dinucleotide phosphate reduced tetrasodium salt (reduced diphosphopyridine nucleotide phosphate sodium salt, NADPH) [2646-71-1] M 833.4, pK as for NADP. Mostly similar to NADH above. 

Section 15.11 Oxidation of alcohols to aldehydes and ketones is a common biological reaction. Most require a coenzyme such as the oxidized form of nicotinamide adenine dinucleotide (NAD" ). 

---