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Nucleoside Monophosphates (nucleoside + monophosphate)
Selected AbstractsMouse RS21-C6 is a mammalian 2,-deoxycytidine 5,-triphosphate pyrophosphohydrolase that prefers 5-iodocytosineFEBS JOURNAL, Issue 6 2009Mari Nonaka Free nucleotides in living cells play important roles in a variety of biological reactions, and often undergo chemical modifications of their base moieties. As modified nucleotides may have deleterious effects on cells, they must be eliminated from intracellular nucleotide pools. We have performed a screen for ITP-binding proteins because ITP is a deaminated product of ATP, the most abundant nucleotide, and identified RS21-C6 protein, which bound not only ITP but also ATP. Purified, recombinant RS21-C6 hydrolyzed several canonical nucleoside triphosphates to the corresponding nucleoside monophosphates. The pyrophosphohydrolase activity of RS21-C6 showed a preference for deoxynucleoside triphosphates and cytosine bases. The kcat/Km (s,1·m,1) values were 3.11 × 104, 4.49 × 103 and 1.87 × 103 for dCTP, dATP and dTTP, respectively, and RS21-C6 did not hydrolyze dGTP. Of the base-modified nucleotides analyzed, 5-I-dCTP showed an eightfold higher kcat/Km value compared with that of its corresponding unmodified nucleotide, dCTP. RS21-C6 is expressed in both proliferating and non-proliferating cells, and is localized to the cytoplasm. These results show that RS21-C6 produces dCMP, an upstream precursor for the de novo synthesis of dTTP, by hydrolyzing canonical dCTP. Moreover, RS21-C6 may also prevent inappropriate DNA methylation, DNA replication blocking or mutagenesis by hydrolyzing modified dCTP. [source] A new chemical method of synthesis of modified nucleoside [32P]phosphatesJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 8 2008D. V. Yanvarev Abstract A simple method of chemical phosphorylation for modified nucleosides with [32P]orthophosphoric acid in the presence of BrCN is described. The yields of 5,-[32P]nucleoside monophosphates achieved are 50,65% at nominal specific radioactivities of ca. 1000,Ci/mmol. The mechanism of phosphorylation in the presence of heterocyclic amines is studied. Copyright © 2008 John Wiley & Sons, Ltd. [source] Expression, purification, crystallization and preliminary X-ray analysis of a nucleoside kinase from the hyperthermophile Methanocaldococcus jannaschiiACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2005Linda Arnfors Methanocaldococcus jannaschii nucleoside kinase (MjNK) is an ATP-dependent non-allosteric phosphotransferase that shows high catalytic activity for guanosine, inosine and cytidine. MjNK is a member of the phosphofructokinase B family, but participates in the biosynthesis of nucleoside monophosphates rather than in glycolysis. MjNK was crystallized as the apoenzyme as well as in complex with an ATP analogue and Mg2+. The latter crystal form was also soaked with fructose-6-phosphate. Synchrotron-radiation data were collected to 1.70,Å for the apoenzyme crystals and 1.93,Å for the complex crystals. All crystals exhibit orthorhombic symmetry; however, the apoenzyme crystals contain one monomer per asymmetric unit whereas the complex crystals contain a dimer. [source] Hydrolytic Reactions of Thymidine 5,- O -Phenyl- N -Alkylphosphoramidates, Models of Nucleoside 5,-Monophosphate ProdrugsCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2007Mikko Ora Dr. Abstract To obtain detailed data on the kinetics of hydrolytic reactions of triester-like nucleoside 5,- O -aryl- N -alkylphosphoramidates, potential prodrugs of antiviral nucleoside monophosphates, the hydrolysis of diastereomeric (RP/SP) thymidine 5,-{O -phenyl- N -[(1S)-2-oxo-2-methoxy-1-methylethyl]phosphoramidate} (3), a phosphoramidate derived from the methyl ester of L -alanine, has been followed by reversed-phase HPLC over the range from H0=0 to pH,8 at 90,°C. According to the time-dependent product distributions, the hydrolysis of 3 proceeds at pH<4 by two parallel routes, namely by nucleophilic displacement of the alaninyl ester moiety by a water molecule and by hydrolysis of the carboxylic ester linkage that allows intramolecular attack of the carboxy group on the phosphorus atom, thereby resulting in the departure of either thymidine or phenol without marked accumulation of any intermediates. Both routes represent about half of the overall disappearance of 3. The departure of phenol eventually leads to the formation of thymidine 5,-phosphate. At pH>5, the predominant reaction is hydrolysis of the carboxylic ester linkage followed by intramolecular displacement of a phenoxide ion by the carboxylate ion and hydrolysis of the resulting cyclic mixed anhydride into an acyclic diester-like thymidine 5,-phosphoramidate. The latter product accumulated quantitatively without any indication of further decomposition. Hydroxide-ion-catalyzed POPh bond cleavage of the starting material 3 occurred as a side reaction. Comparative measurements with thymidine 5,-{N -[(1S)-2-oxo-2-methoxy-1-methylethyl]phosphoramidate} (4) revealed that, under acidic conditions, this diester-like compound is hydrolyzed by PN bond cleavage three orders of magnitude more rapidly than the triester-like 3. At pH>5, the stability order is reversed, with 3 being hydrolyzed six times as rapidly as 4. Mechanisms of the partial reactions are discussed. [source] Aryloxy Phosphoramidate Triesters: a Technology for Delivering Monophosphorylated Nucleosides and Sugars into CellsCHEMMEDCHEM, Issue 11 2009Youcef Mehellou Dr. Abstract Prodrug technologies aimed at delivering nucleoside monophosphates into cells (protides) have proved to be effective in improving the therapeutic potential of antiviral and anticancer nucleosides. In these cases, the nucleoside monophosphates are delivered into the cell, where they may then be further converted (phosphorylated) to their active species. Herein, we describe one of these technologies developed in our laboratories, known as the phosphoramidate protide method. In this approach, the charges of the phosphate group are fully masked to provide efficient passive cell-membrane penetration. Upon entering the cell, the masking groups are enzymatically cleaved to release the phosphorylated biomolecule. The application of this technology to various therapeutic nucleosides has resulted in improved antiviral and anticancer activities, and in some cases it has transformed inactive nucleosides to active ones. Additionally, the phosphoramidate technology has also been applied to numerous antiviral nucleoside phosphonates, and has resulted in at least three phosphoramidate-based nucleotides progressing to clinical investigations. Furthermore, the phosphoramidate technology has been recently applied to sugars (mainly glucosamine) in order to improve their therapeutic potential. The development of the phosphoramidate technology, mechanism of action and the application of the technology to various monophosphorylated nucleosides and sugars will be reviewed. [source] | ||||||||||