Diphosphopyridine nucleotide and

Fio. 7.—Tentative Mechanism for the Enzymic Conversion of 3-Deoxy-n-aro5mo-heptulosonic Acid 7-Phoaphate to 6-Dehydroquinic Acid. (DPN denotes diphosphopyridine nucleotide and DPNH is reduced diphosphopyridine nucleotide.)... 

Salganicoff L, Koeppe RA (1968) Subcellular distribution of pyruvate carboxylase, diphosphopyridine nucleotide and triphosphopyridine nucleotide isocitrate dehydrogenases, and malate enzyme in rat brain. J Biol Chem 243 .34l6-3420. 

G. DiSabato (1970), Adducts of diphosphopyridine nucleotide and carbonyl compounds. Biochemistry 9, 4594-4600. 

Diphosphopyridine nucleotide and analogous quaternary pyridinium salts form complexes with bisulphite and with thiols 2-5, xhe orientation of these additions is usually uncertain and may vary with the reaction solvent used " 4, The dithionite addition products formed by quaternary pyridinium salts have attracted interest because of their connection with the dithionite reduction of diphosphopyridine nucleotide (p. 259). Thus, the formation of a 1,4-dihydropyridine (122) by reduction of (120) has been represented 6 as proceeding through a 1,2-addition product (121). Regardless of the correctness or otherwise of structure (121), the relevance of the intermediate for diphosphopyridine nucleotide reduction by dithionite has been questioned, and the yellow intermediate formed in this reaction has been formulated 8 as a charge-transfer complex between the pyridinium nucleus and 820 (see p. 261). 

Komberg, A., 1950, Reversible enzymatic synthesis of diphosphopyridine nucleotide and inorganic pyrophosphate, 7. Biol. Chem. 182 779-793. 

SCHELLENBERG, K. A. Evidence for the Participation of Tryptophan as Intermediate in Transfer of Hydrogen between Diphosphopyridine Nucleotide and Substrate in Yeast Alcohol Dehydrogenase. J. Biol. Chem. 240, 1165-1169 (1965). 

N4. Nordin, J. H., and Bretthauer, R. K., Colorimetric detection of carriers of galactosemia based on thionicotinamide diphosphopyridine nucleotide (TNDPN) reduction. Federation Proc. 20, 256 (1961). 

The reduction of aromatic nitro compQunds (see p. 98) is also due to the action of an enzyme system in which a dehydrogenase transfers hydrogen to a diphosphopyridine nucleotide-flavoprotein, which in turn reduces the nitro group (Westfall, as well as Bueding and Jolliffe ). 

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 splitting of sugar to lactic acid is thus, briefly, the shifting of hydrogen by means of the nicotinamide moiety of diphosphopyridine nucleotide (also termed nicotinamide adenine dinuclcotide). Nicotinamide in DPN takes away two atoms of hydrogen from phosphorylated carbohydrate, and after dephosphorylation gives back two hydrogens fin DPNH ) to pyruvic acid. 

The toxic action of bilirubin on tissue metabolism has been demonstrated both by in vitro and in vivo experiments. Lathe (LI) added bilirubin to brain brei, in concentrations such as occur in hemolytic disease of the newborn and prematurity, and observed a decrease in oxygen consumption. Day (D3) was able to reverse this depressed respiration by the addition of cytochrome c or methylene blue. Bowen and Waters (B16) then showed that this reversal could also be efFected by diphosphopyridine nucleotide. Zetterstrom and Ernster (Zl), using isolated rat liver mitochondria, showed that bilirubin in concentrations... 

Boyer, P.D. and Theorell, H. The change in reduced diphosphopyridine nucleotide (DPNH) fluorescence upon combination with liver alcohol dehydrogenase (ADH). Acta Chem. Scand., 10 447-450, 1956. 

Winer, A.D., Schwert, G.W. and Millar, D.B.S. Lactic dehydrogenase. VI. Fluorometric measurements of the complex of enzyme and reduced diphosphopyridine nucleotide. 

The conversion of 3-deoxy-D-am6mo-heptulosonic acid 7-phosphate to 5-dehydroquinate was also abolished by the chelating agent (ethylenedi-nitrilo)tetracetate, and could be restored partially by Zn and completely by Co . Occasionally, carbon-treated preparations could not be reactivated by diphosphopyridine nucleotide alone only by the further addition of cobaltous salts was activity restored. Attempts to acciunulate an intermediate by omitting, from such extracts, either diphosphop dine nucleotide or Co were not successful, and, unless both of these were simultaneously present, the 3-deoxy-D-oroWno-heptulosonic acid 7-phosphate remained xmchanged. 

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. 

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