Triphosphopyridine nucleotide coenzyme

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... 

Pure NADP+ was isolated from red blood cells in 1934 by Otto Warburg and W. Christian, who had been studying the oxidation of glucose 6-phosphate by erythrocytes.13 They demonstrated a requirement for a dialyzable coenzyme which they characterized and named triphosphopyridine nucleotide (TPN+, but now officially NADP+ Fig. 15-1). Thus, even before its recognition as an important vitamin in human nutrition, nicotinamide was identified as a component of NADP+. 

Analogous results have been obtained in the electrolysis of the pyridine nucleotides134-141 the dimer has, however, been suggested to be a 4,4 -dimer.139 The coenzyme activity of the reduction product varies with the experimental conditions. Some reductions yielded totally inactive products, whereas others produced partly or fully active material. The highest activity was obtained by an indirect electrolytic reduction of triphosphopyridine nucleotide (TPN).141 Electrochemical reduction of methyl viologen in the presence of ferridoxin-TPN-reductase caused a reduction of TPN to a biochemically active product. 

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. 

The adenosine phosphates (AMP, ADP, ATP) are relatively unstable in solution. At 100 in dilute add the two anhydride bonds of ATP are split but the ester linkage remains intact. In AMP the esterification of the adenosine is on C-5 of the sugar whilst in other nucleotides (coenzyme A, triphosphopyridine-nucleotide) other carbon atoms are involved. 

NADP is known as triphosphopyridine nucleotide (TPN), coenzyme II, Warburg s coferment, codehydrogenase II, cozymase II, and phosphocozymase. NADP (C21H28N7O17P3, molecular weight 743.44) (inner salt) is a grayish-white powder. It is soluble in water and in methanol, but much less soluble in ethanol and practically insoluble in diethyl ether and ethyl acetate. 

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. 

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). 

By recent, official recommendation (see Chapt. VI-4) the two hydrogen-transferring coenzymes, formerly known as di- and triphosphopyridine nucleotide (abbreviated as DPN and TPN) are, to be called nicotinamide-adenine dinucleotide (NAD) and nicotinamide-adenine dinucleotide phosphate (NADP). The new nomenclature offers greater correctness and consistency, among other advantages. 

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

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