Diphosphopyridine nucleotide Coenzyme

Nicotinamide adenine dinucleotide reduced disodium salt trihydrate (reduced diphosphopyridine nucleotide sodium salt, NADH) [606-68-8/ M 763.5. This coenzyme is available in high purity and it is advised to buy a fresh preparation rather than to purify an old sample as purification will invariably lead to a more impure sample contaminated with the oxidised form (NAD). It has... 

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... 

The reduced form of the respiratory coenzyme diphosphopyridine nucleotide (DPNH), which is vitally important for all cellular metabolism, is changed by dilute acid to a substance that, in the light of the following model experiments, may be a covalent hydrate. The 1,4-and 1,6-dihydro derivatives of l-benzylpyridine-3-carboxamide furnish a single substance when dissolved in dilute acid at 20° and the solution is basified. The stable yellow product, which has a prominent peak at 292 nm, was assigned the constitution 1-benzyl-6-hydroxy-1,4,5,6-tetra-hydropyridine-3-carboxamide61 (see Scheme 2). 3-Acetyl-1 -benzyl- 1,4-... 

Increased interest is added to the topic of this review by the discovery of several examples of covalent hydration in nature although no systematic investigation has been made, an increasing alertness to its possible occurrence can be detected among natural product workers. Some naturally occurring pteridines, such as xanthopterin,67 are covalently hydrated. The hydration of uracil and of the coenzyme diphosphopyridine nucleotide (DPNH) were mentioned in Section IV. 

The nicotinamide coenzymes are involved as proton and electron carriers in a wide variety of oxidation and reduction reactions. Before their chemical structures were known, NAD and NADP were known as coenzymes I and II. Later, when the chemical nature of the pyridine ring of nicotinamide was discovered, they were called diphosphopyridine nucleotide (DPN = NAD) and triphospho-pyridine nucleotide (TPN = NADP). The nicotinamide nucleotide coenzymes are sometimes referred to as the pyridine nucleotide coenzymes. 

The irradiation of coenzyme I (diphosphopyridine nucleotide) results in reduction of the pyridine-carbox-amido ring. The product of this reduction is probably a dimer that is itself radiosensitive. 

Reduction of a-diketones and a-keto esters. Nicotinamide is a component of the coenzymes diphosphopyridine nucleotide (DPN) and triphosphopyridine... 

Among the spectra of coenzymes given by Rosenkrantz were glutathione (reduced and oxidized), diphosphopyridine nucleotide (DPN or NAD ) and its reduced form (Na salt), triphosphopyridine nucleotide and its reduced form (Na salt), flavin mononucleotide, flavin adenine dinucleotide, oxidized cytochrome c (containing some of the reduced form), and thiamine pyrophosphate. 

It would be well to point out a few examples which illustrate the overlap of asymmetric reduction studies and molecular biochemistry. Diphosphopyridine nucleotide (DPN) and triphospho-pyridine nucleotide (TPN) are important coenzymes in biochemical oxidation reduction reactions. Certain enzymes function as catalysts for the reversible transfer of hydrogen between these nucleotides and a substrate for which the enzyme is specific. For example, DPN and the enzyme, alcohol dehydrogenase (ADH), form a redox system with ethanol. Using deuterium labeled reducing agent and substrate, Westheimer, Vennesland,... 

The following abbreviations will be used in this article. ATP = adenosine triphosphate ADP — adenosine diphosphate DPNox oxidized diphosphopyri-dine nucleotide DPNred = reduced diphosphopyridine nucleotide CoA or CoA—SH = coenzyme A CoA—S—COCH3 = acetyl-coenzyme A FAD = flavin adenine dinucleotide R—P = low-energy phosphate bond R P = high-energy bond Pi = inorganic orthophosphate. 

In 1931 Otto Warburg discovered that the oxidation of glucose 6-phosphate in red blood cells required both an enzyme and a heat stable coenzyme, and he later referred to the latter as the Wasserstolfubertragendes Co-Ferment , i> to distinguish it from cozymase, the coenzyme of yeast fermentation, which had been discovered many years earlier by Sir Arthur Harden. He found that the functional group in both coenzymes was nicotinamide, which acted as acceptor for the protons removed from the substrate. In addition to nicotinamide, each coenzyme also contained one adenine and two ribosyl residues, but they differed in their phosphorus content. These observations led him to name the cozymase diphosphopyridine nucleotide (DPN), and the hydrogen-transferring coenzyme tri-phosphopyridine nucleotide (TPN). ... 

NAD+ has been designated as diphosphopyridine nucleotide (DPN), coenzyme I, factor V, codehydrogenase I, Harden s coferment, cozymase I, and codihydrase. NAD+ (C21H27O14P2, molecular weight 663.4) (inner salt) is a very hydroscopic white powder and is freely soluble in water. A 1 % solution has a pH of about 2. 

In 1935, von Euler, Albers, and Schlenck studied the preparation of cozymeise, the coenzyme which is necessary for the alcoholic fermentation of glucose by apozymase, shown later to be diphosphopyridine nucleotide (DPN). On hydrolysis, cozymeise yielded nictotinic acid. This was the first evidence that nicotinic acid (in the form of its amide) formed a part of the structure of an enzyme, and placed it among the organic compounds of great importance in biological chemistry. 

In addition to their role as components of nucleoproteins, purines and pyrimidines are vital to the proper functioning of the cell. The bases are constituents of various coenzymes, such as coenzyme A (CoA), adenosine triphosphate (ATP), guanosine triphosphate (GTP), cytidine triphosphate (CTP), diphosphopyridine nucleotide (DPN), triphosphopyridine nucleotide (TPN), and flavin adenine dinucleotide (FAD). A pyrimidine derivative, cytidine diphosphate choline, is involved in phospholipid synthe another pyrimidine compound, uridine diphosphate glucose, is an important substance in carbohydrate metabolism. Cytidine diphosphate ribitol functions in the biosynthesis of a new group of bacterial cell-wall components, the teichoic acids. While mammals excrete nitrogen derived from protein catabolism in the form of urea, birds eliminate their nitrogen by synthesizing it into the purine compound, uric acid. 

The mechanism of synthesis of flavin adenine dinucleotide was established by Schrecker and Komberg 1S6) with a purified enzyme from brewer s yeast. The coenzyme is formed by a reaction analogous to the synthesis of diphosphopyridine nucleotide (1S7). 

The S -phosphates of deoxyribosyl adenine, etc. Adenosine diphosphate Adenosine triphosphate Nicotinamide mononucleotide Diphosphopyridine nucleotide (cozymase, coenzyme I)... 

There are two different enzymes, distinguishable among other things by their coenzymes. The normal terminal breakdown reaction relies chiefly on the NAD-dependent enzyme. Again, we would like to draw attention to the change in nomenclature The nicotinamide coenzymes formerly were known as diphosphopyridine nucleotide (DPN) and triphosphopyridine nucleotide (TPN). 

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