Diphosphopyridine nucleotide, oxidation

ADH Antidiuretic hormone, vasopressin DPN+ Diphosphopyridine nucleotide (oxidized)... 

The reduced form of diphosphopyridine nucleotide (DPNH), which is used in the reduction of di-O-phosphoglyceronic acid to O-phosphoglycerose, could be regenerated with high efficiency from the oxidized form (DPN ) by the reduced form of 6-thioctic acid, thus supplying the necessary re-... 

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 ring of anthranilic acid, like that of prephenic acid, is derived, in appropriate bacterial extracts, from shikimate 5-phosphate, the amino group originating in the amide nitrogen of glutamine. An oxidation-reduction appears to be involved in this synthesis, since diphosphopyridine nucleotide is a required cofactor. At least one other cofactor, present in yeast extract and so far unidentified, is also required. 

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. 

Aldol dehydrogenases, from diverse species including yeast, horses and humans, catalyze the oxidation of ethanol or the reduction of acetaldehyde, using diphosphopyridine nucleotide (DPN) as a co-factor. Crystalline yeast alcohol dehydrogenase has a molecular weight of 150,000 and contains four Zn2+ ions and binds four DPN molecules per mole. Its structure and chemistry are not yet known in detail. 

According to investigations by Theorell 54), the oxidation of alcohol by alcohol dehydrogenase from liver involves a binary complex of dehydrogenase -h diphosphopyridine nucleotide (DPN), while with yeast dehydrogenase the complex is ternary and includes the alcohol. Vennesland and Westheimer 55) have established, using deuteroethanol with yeast alcohol dehydrogenase, that the reaction is... 

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,... 

It is likely that the hydrogen from XH2 dissociates into a hydride ion H (= H+ + 2 e ) and a proton, H+. The oxidized diphosphopyridine nucleotide then combines with the hydride ion leaving the proton in solution as hydrogen ion. These reactions can be summarized as follows ... 

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). ... 

Lehninger, a. L. (1951) Phosphorylation coupled to oxidation of diphosphopyridine nucleotide. /. Biol. Chem. 190, 345-359. 

The first clear-cut effect of an estri enic hormone added in vitro to an enzyme system was reported by Hagerman and Villee (1953) and Villee and Hagerman (1953), who showed that the addition of estradiol-17/3 to slices of human endometrium or placenta incubated in vitro produced an increased rate of oxidative metabolism. In placental homogenates the locus of action of estradiol was considered to be a diphosphopyridine nucleotide-linked isocitric dehydrogenase present in the soluble fraction (Villee and Gordon, 1955). Triphosphopyridine nucleotide did not replace diphosphopyridine nucleotide (Villee, 1955), and a divalent metal cation is required for full... 

Ueda T, Lode ET, Coon MJ. 1972. Enzymatic omega-oxidation, 6 isolation of homogeneous reduced diphosphopyridine nucleotide-rubredoxin reductase. J Biol Chem 247 2109-2116. 

In similar circumstances l-(2,6-dichlorobenzyl)pyridinium bromide is said to give a salt (88), which can be oxidized to the methide (89). Several such reactions are known Closely related are those of diphosphopyridine nucleotide with carbonyl compounds in alkali 35 ... 

Rodkey FL. Oxidation-reduction potentials of the diphosphopyridine nucleotide system. J Biol Chem 1955 213 777-786. 

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