Nucleoside diphosphate phosphorylation

All of these triphosphates take part in phosphorylations in the cell. Similarly, specific nucleoside monophosphate kinases catalyze the formation of nucleoside diphosphates from the corresponding monophosphates. 

While mammahan cells reutilize few free pyrimidines, salvage reactions convert the ribonucleosides uridine and cytidine and the deoxyribonucleosides thymidine and deoxycytidine to their respective nucleotides. ATP-dependent phosphoryltransferases (kinases) catalyze the phosphorylation of the nucleoside diphosphates 2 "-de-oxycytidine, 2 -deoxyguanosine, and 2 -deoxyadenosine to their corresponding nucleoside triphosphates. In addition, orotate phosphoribosyltransferase (reaction 5, Figure 34-7), an enzyme of pyrimidine nucleotide synthesis, salvages orotic acid by converting it to orotidine monophosphate (OMP). 

Deoxynucleotides for DNA synthesis are made at the nucleoside diphosphate level and then have to be phosphorylated up to the triphosphate using a kinase and ATP. The reducing equivalents for the reaction come from a small protein, thioredoxin, that contains an active site with two cysteine residues. Upon reduction of the ribose to the 2 -deoxyri-bose, the thioredoxin is oxidized to the disulfide. The thioredoxin(SS) made during the reaction is recycled by reduction with NADPH by the enzyme thioredoxin reductase. 

The subsequent cleavage of the thio-ester succinylCoA into succinate and coenzyme A by succinic acid-CoA ligase (succinyl CoA synthetase, succinic thiokinase) is strongly exergonic and is used to synthesize a phosphoric acid anhydride bond ( substrate level phosphorylation , see p. 124). However, it is not ATP that is produced here as is otherwise usually the case, but instead guanosine triphosphate (CTP). However, GTP can be converted into ATP by a nucleoside diphosphate kinase (not shown). 

The synthesis of purine nucleotides (1) starts from IMP. The base it contains, hypoxanthine, is converted in two steps each into adenine or guanine. The nucleoside monophosphates AMP and CMP that are formed are then phos-phorylated by nucleoside phosphate kinases to yield the diphosphates ADP and GDP, and these are finally phosphorylated into the triphosphates ATP and CTP. The nucleoside triphosphates serve as components for RNA, or function as coenzymes (see p. 106). Conversion of the ribonucleotides into deoxyribo-nucleotides occurs at the level of the diphosphates and is catalyzed by nucleoside diphosphate reductase (B). 

This enzyme [EC 2.7.1.74] catalyzes the reaction of a nucleoside triphosphate with deoxycytidine to produce a nucleoside diphosphate and dCMP. This enzyme can use any nucleoside triphosphate (except dCTP) as the phosphate-donor substrate and it can phosphorylate cytosine arabinoside as well. 

S Additional information <5, 7, 11, 25> (<5,7,11 > in the absence of nucleoside diphosphates the enzyme undergoes Mg -dependent stoichiometric autophosphorylation using ATP, GTP or y-thiotriphosphate as phosphate donor, 2 mol phosphate per mol enzyme [12] <25> autophosphorylation and phosphorylation of histone Hl [19] <31> strong preference for d-enantiomers of antiviral nucleotide analogs like ddATP, ddCTP, 3 -deoxy-3 -thymidine, 2 ,3 -didehydro-2 ,3 -dideoxythymidine [50]) [12, 19, 50]... 

Schneider, B. Babolat, M. Xu, Y.W. Janin, J. Veron, M. Deville-Bonne, D. Mechanism of phosphoryl transfer by nucleoside diphosphate kinase pH dependence and role of the active site Lysl6 and Tyr56 residues. Eur. J. Biochem., 268, 1964-1971 (2001)... 

Bourdais, J. Biondi, R. Sarfati, S. Guerreiro, C. Lascu, L Janin, J. Veron, M. Cellular phosphorylation of anti-HIV nucleosides. Role of nucleoside diphosphate kinase. J. Biol. Chem., 271, 7887-7890 (1996)... 

D. Herschlag, D. Nucleophilic activation by positioning in phosphoryl transfer catalyzed by nucleoside diphosphate kinase. Biochemistry, 38, 4701-4711 (1999)... 

ATP is the primary high-energy phosphate compound produced by catabolism, in the processes of glycolysis, oxidative phosphorylation, and, in photosynthetic cells, photophosphorylation. Several enzymes then cany phosphoryl groups from ATP to the other nucleotides. Nucleoside diphosphate kinase, found in all cells, catalyzes the reaction... 

FIGURE 13-12 Ping-Pong mechanism of nucleoside diphosphate kinase. The enzyme binds its first substrate (ATP in our example), and a phosphoryl group is transferred to the side chain of a His residue. ADP departs, and another nucleoside (or deoxynucleoside) diphos-... 

The formation of ATP (or GTP) at the expense of the energy released by the oxidative decarboxylation of a-ketoglutarate is a substrate-level phosphorylation, like the synthesis of ATP in the glycolytic reactions catalyzed by glyceraldehyde 3-phosphate dehydrogenase and pyruvate kinase (see Fig. 14-2). The GTP formed by succinyl-CoA synthetase can donate its terminal phosphoryl group to ADP to form ATP, in a reversible reaction catalyzed by nucleoside diphosphate kinase (p. 505) ... 

Most kinases transfer chiral phospho groups with inversion and fail to catalyze partial exchange reactions that would indicate phosphoenzyme intermediates. However, nucleoside diphosphate kinase contains an active site histidine which is phosphorylated to form a phosphoenzyme.869 The enzyme catalyzes phosphorylation of nucleoside diphosphates other than ADP by a nucleotide triphosphate, usually ATP. 

Choline and ethanolamine are activated in much the same way as are sugars. For example, choline can be phosphorylated using ATP (Eq. 17-58, step a) and the phosphocholine formed can be further converted (Eq. 17-58, step b) to cytidine diphosphate choline. Phosphocholine is transferred from the latter onto a suitable acceptor to form the final product (Eq. 17-58, step c). Tire polymerization pattern differs from that for polysaccharide synthesis. When the sugar nucleotides react, the entire nucleoside diphosphate is eliminated (Eq. 17-56), but CDP-choline and CDP-ethanolamine react with elimination of CMP (Eq. 

Polyphosphate kinase has been found able to phosphorylate nucleoside diphosphates to give nucleoside triphosphates, using PolyP as a phosphate donor. Therefore, the possibility of using PolyP and polyphosphate kinase instead of phosphoenol pyruvate and pyruvate kinase for enzymatic oligosaccharide synthesis was examined, because PolyP is quite cheap when compared with phosphoenol pyruvate (Noguchi and Shiba, 1998 Shiba et al, 2000). Attempts were made to synthesize N-acetyllactosamine (Gal (f> 1-4) GlcNAc) using the nucleoside diphosphate kinase-like activity of polyphosphate kinase, where UDP-Glc pyrophosphorylase and UDP-Glc 4-epimerase catalyse the synthesis of UDP-Glc from... 

Nucleoside diphosphate kinase is relatively nonspecific enzyme that transfers a phosphoryl group from a variety of nucleoside triphosphates to nucleoside diphosphates. Its biological function is presumably to use ATP to phosphoryl-ate the various ribo- and deoxyribonucleoside diphosphates to form the triphosphate derivatives need by the cell. 

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