Nicotinamide nucleotides

Nicotinamide Nucleotides.— The reaction between phosphorothioates and disilver salts of phosphoric acids has been used to synthesize FAD, UDPGlc, and UDPGal in high yield. An advantage of this method is that by-products such as symmetrical pyrophosphates are not formed. 

Simple procedures for the preparation of NMN+ by chemical or enzymic methods have been reported and although the phosphorylating agent metaphosphoric acid used in the chemical phosphorylation of nicotinamide 2, 3 -0-isopropylidene ribofuranoside is relatively imsophisticated, the synthesis can be carried out on a large scale with moderate yields. The stereo- 

The drug most commonly used to treat Trichomonas vaginalis and some entamoebal infections, l-(2-hydroxyethyl)-2-methyl-5-nitroimidazole [Flagyl, (3)] can also produce an aversion to ethanol in patients. It has now been shown that while (3) will displace the nicotinamide moiety of NAD+ or NADP+ in the presence of pyridine transglycosidase to produce new nucleotides, there is no reaction between (3) and NADH. It is not, however, believed that the toxicity towards anaerobic organisms is due to the new adenosine pyrophosphates derived from (3). 

Two new derivatives of NAD+ have been prepared for the purification of dehydrogenases by affinity chromatography. In these derivatives the adenine residue is joined at the 6-position to an insoluble support by means of a spacer 

Nicotinamide Nucleotides.—A number of dehydrogenases have been purified by affinity chromatography, using NAD+ linked to insoluble supports either through the 6-11)12 or the 8-positions13 of the adenine nucleus. The reverse process, the use of immobilized dehydrogenases to purify NAD+, has also been described recently.14 

The binding of NAD+ or NADH to lactate18 or D-glyceraldehyde 3-phosphate19 dehydrogenases involves the pyrophosphoryl group. Data recently obtained from 31P n.m.r. of these enzymes show that the environments of the pyrophosphoryl group 

Glyceraldehyde 3-phosphate dehydrogenase catalyses the hydration of NADH to a new product (NADHX), which has the same spectroscopic properties as one of the 

In strong alkali, NAD+ reacts with opening of the nicotinamide ring to give a 

Schiflf base that has been assigned the structure (6).2 The formation of this intermediate may play some part in the binding of NAD+ to dehydrogenases. 

Reagents i, DCC in DMF ii, D-pantethine-4, 4 -diphosphate in acetic acid-pyridine 

Taguchi, N. Noriyuki, T. Kakimoto, and Y. Mushika, Bull. Chem. Soc. Japan, 1976, 49, 1122. 

Since most dehydrogenases, save for alcohol dehydrogenase, do not contain metals, the necessary polarization of the oxidized substrate must be carried out in another manner. For lactate dehydrogenase, X-ray analysis reveals that the imidazolium group of His 195 appears to 

Two important reactions involving coenzyme A are worthy of mention the first is the oxidative decarboxylation of pyruvate to acetyl-coenzyme A, which is catalyzed by the multienzyme complex, pyruvate dehydrogenase. This reaction involves a series of steps mediated by five coenzymes, during which a series of acid-base reactions and nucleophilic displacements take place, with pyruvate being oxidized and converted to acetyl-CoA. Another essential series of reactions involving acetyl-CoA is that of fatty acid synthesis. Here acetyl-CoA is converted to malonyl-CoA through condensation of the enzyme-bound thioester, with the occurrence of simultaneous decarboxylation. 

---

In contrast to the nicotinamide nucleotide dehydrogenases, the prosthetic groups FMN and FAD are firmly associated with the proteins, and the flavin groups are usually only separated from the apoen2yme (protein) by acid treatment in water. However, in several covalently bound flavoproteins, the enzyme and flavin coen2ymes are covalently affixed. In these cases, the flavin groups are isolated after the proteolytic digestion of the flavoproteins. 

Subjecting cells to oxidative stress can result in severe metabolic dysfunctions, including peroxidation of membrane lipids, depletion of nicotinamide nucleotides, rises in intracellular free Ca ions, cytoskeletal disruption and DNA damage. The latter is often measured as formation of single-strand breaks, double-strand breaks or chromosomal aberrations. Indeed, DNA damage has been almost invariably observed in a wide range of mammalian cell types exposed to oxidative stress in a number... 

In accordance with the recommendation of the Commission of the International Union of Biochemistry [R. H. S. Thompson, Classification and nomenclature of enzymes and coenzymes, Nature 193, 1227 (1902)] the terms NAD and NADP have been used instead of DPN and TPN, except in Fig. 4. The generic term nicotinamide nucleotides is used with the same significance as pyridine nucleotides. 

J. London and M. Knight, Concentrations of nicotinamide nucleotide coenzymes in micro-organisms, J. Gen. Microbiol. 44, 241-254 (1966). 

D. E. F. Harrison and B. Chance, Fluorimetric technique for monitoring changes in the level of reduced nicotinamide nucleotides in continuous cultures of microorganisms, Appl. Microbiol. 19, 446-450 (1970). 

N-dealkylation results from an alkyl substitution on an aromatic molecule, which is one of the first places where microorganisms initiate catabolic transformation of atrazine, a xenobiotic molecule (Fig. 15.2). It is a typical example of a reaction leading to transformation of pesticides like phenyl ureas, acylanihdes, carbamates, s-tri-azines, and dinitranilines. The enzyme mediating the reaction is a mixed-function oxidase, requiring a reduced nicotinamide nucleotide as an H donor. 

DNA ligase (NAD+) [EC 6.5.1.2] (also referred to as polydeoxyribonucleotide synthase (NAD+), polynucleotide ligase (NAD+), DNA repair enzyme, and DNA join-ase) catalyzes the reaction of NAD+ with (deoxyribo-nucleotide) and (deoxyribonucleotide) to produce AMP, nicotinamide nucleotide, and (deoxyribonucleo-tide)( +m). This forms a phosphodiester at the site of a single-strand break in duplex DNA. RNA can also act as substrate to some extent. 

This enzyme [EC 1.6.1.1] (also known as NAD(P)+ trans-hydrogenase (B-specific), pyridine nucleotide transhy-drogenase, and nicotinamide nucleotide transhydro-genase) catalyzes the reversible reaction of NADPH with NAD+ to produce NADP+ and NADH. This FAD-dependent enzyme is B-specific with respect to both pyridine coenzymes. In addition, deamino coenzymes will also serve as substrates. 

Nicotinamide nucleotide transhydrogenase, NADfPj TRANSHYDROGENASE NICOTINAMIDE PHOSPHORIBOSYLTRANS-FERASE... 

Youssef NN, Hammond D (1971) The fine structure of the developmental stages of the microsporidian Nosema apis Zander. Tissue Cell 3 283-294 Yu Y, Samuelson J (1994) Primary structure of an Entamoeba histolytica nicotinamide nucleotide transhydrogenase. Mol Biochem Parasitol 68 323-328 Zheng L, Cash VL, Hint DH, Dean DR (1998) Assembly of iron-sulfur clusters. Identification of an iscSUA-hscBA-fdx gene cluster from Azotobacter vinelandii. J Biol Chem 273 13264-13272... 

Nicotinamide adenine dinucleotide (NAD+ in its oxidized form) and its close analog nicotinamide adenine dinucleotide phosphate (NADP+) are composed of two nucleotides joined through their phosphate groups by a phosphoanhydride bond (Fig. 13-15a). Because the nicotinamide ring resembles pyridine, these compounds are sometimes called pyridine nucleotides. The vitamin niacin is the source of the nicotinamide moiety in nicotinamide nucleotides. 

Oxidative phosphorylation begins with the entiy of electrons into the respiratory chain. Most of these electrons arise from the action of dehydrogenases that collect electrons from catabolic pathways and funnel them into universal electron acceptors—nicotinamide nucleotides (NAD+ or NADP+) or flavin nucleotides (FMN or FAD). 

Nicotinamide nucleotide-linked dehydrogenases catalyze reversible reactions of the following general types ... 

J. B. Hoek and J. Rydstrom, Physiological roles of nicotinamide nucleotide transhy-drogenase, Biochem. J. 254 1 (1988). 

M Anderlund, TL Nissen, J Nielsen, J Villadsen, J Rydstrom, B Hahn-Hagerdal, MC Kielland-Brandt. Expression of the Escherichia coli pntA and pntB genes, encoding nicotinamide nucleotide transhydrogenase, in Saccharomyces cerevisiae and its effect on product formation during anaerobic glucose fermentation. Appl Environ Microbiol 65 2333-2340, 1999. 

Nicotinamide nucleotide (NAD, NADP, NADH, NADPH) levels (Table 4.6) have been measured only in one cestode, H. diminuta (42), which probably reflects the difficulty of carrying out such an analysis. In this... 

Table 4.6. The levels of nicotinamide nucleotides in Hymenolepis diminuta compared with Fasciola hepatica and Ascaris... 

The term nicotinamide nucleotide transhydrogenase (EC 1.6.1.1) is used in this chapter to denote those enzymes that catalyze the reversible... 

Nicotinamide nucleotide transhydrogenases may be divided into two classes. One class is present in certain bacteria, and possibly in some plants, is an easily extractable, water-soluble enzyme is not functionally linked to the energy-transfer system of the bacterial membrane is a fiavoprotein and is specific for the 4B-hydrogen atom of both NADH and NADPH. The other class is present in both certain bacteria and in mitochondria is a firmly membrane-bound water-insoluble enzyme is functionally linked to the energy-transfer system of the bacterial or mitochondrial membrane is not known to be a flavoprotein and is specific for the 4A-hydrogen atom of NADH and the 4B-hydrogen atom of NADPH. For the sake of convenience, the two classes of enzyme will be referred to below as BB-specific and AB-specific transhydrogenases, respectively. 

Nicotinamide nucleotide transhydrogenase was originally discovered in Pseudomonas fluorescens. Part of the work done with these bacteria by Kaplan and co-workers (see 7) appeared later to have involved Pseudomonas aeruginosa. There is little doubt, however, that these two strains contain transhydrogenases that are closely related. Kaplan and co-workers (5) also demonstrated the presence of transhydrogenase in... 

The kinetic properties (see Section II,E) and spectral characteristics (7, 9, 10, 17, 19) of the BB-specific transhydrogenases strongly suggest that these enzymes are fiavoproteins. Consistent with this suggestion, Louie and Kaplan (7) showed that, in the presence of 1 M urea, was taken up from the medium and was incorporated into the reduced nicotinamide nucleotide. Direct proof for the occurrence of FAD in both the... 

Pseudomonas and Azotobacter transhydrogenases was provided by Cohen and Kaplan (17) and by van den Broek et al. [19), respectively, who showed that inactivation by heat treatment could be reversed by addition of FAD. FAD could not be replaced by FMN. Reduction of the enzyme with either NADH or NADPH largely increased the heat sensitivity, whereas oxidized nicotinamide nucleotides or FAD had the opposite effect (17, 19). The number of flavins per 50,000-dalton molecular weight was calculated to be 0.58 to 1.1 (17). 

In addition to transfer of hydrogen between various nicotinamide nucleotides, the transhydrogenases from Pseudomonas 17), spinach 11, 13), and Azotobacter 9, 19) also catalyze a diaphorase reaction, using either NADH or NADPH plus an artificial acceptor, e.g., potassium fer-ricyanide or dichlorophenolindophenol. As expected, 2 -AMP stimulates the NADH-linked diaphorase reaction catalyzed by the Pseudomonas enzyme 17). 

---