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Adenosine Kinase (adenosine + kinase)
Terms modified by Adenosine Kinase Selected AbstractsSearching Inhibitors of Adenosine Kinase by Simulation MethodsCHINESE JOURNAL OF CHEMISTRY, Issue 11 2006Rui-Xin Zhu Abstract Searching new inhibitors of adenosine kinase (AK) is still drawing attention of experimental scientists. A better and solid model is here proposed by means of simulation methods from different ways, the direct analysis of receptor itself, the conventional 3D-QSAR methods and the integration of docking method and the conventional QSAR analysis. [source] Substrate analogs induce an intermediate conformational change in Toxoplasma gondii adenosine kinaseACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2007Yan Zhang Adenosine kinase (AK) is a key enzyme in purine metabolism in the ubiquitous intracellular parasite Toxoplasma gondii and is a potential chemotherapeutic target for the treatment of T. gondii infections. To better understand the structure,activity relationship of 6-substituted purine ribosides, the structures of the T. gondii AK,N6,N6 -dimethyladenosine (DMA) complex, the AK,DMA,AMP-PCP complex, the AK,6-methyl mercaptopurine riboside (MMPR) complex and the AK,MMPR,AMP-PCP complex were determined to 1.35, 1.35, 1.75 and 1.75,Å resolution, respectively. These structures reveal a conformation intermediate between open and closed, with a small lid-domain rotation of 12°. Residues Gly143- X - X -Gly146 undergo torsional changes upon substrate binding, which together with a Gly68-Gly69 switch induces a hinge bending of the lid domain. The intermediate conformation suggests that ATP binding is independent of adenosine binding. Orienting the ,-phosphate group of ATP into the optimal catalytic position may be the last step before the onset of chemical catalysis and may require the translocation of Arg136 following the complete closure of the lid domain. 6-Substituted purine-nucleoside analogs are accommodated in a hydrophobic cavity. Modification at the N6 or C6 position of the nucleoside would affect the interactions with the surrounding residues and the binding affinity. [source] Adenosine downregulates cytokine-induced expression of intercellular adhesion molecule-1 on rheumatoid synovial fibroblasts independently of adenosine receptor signalingDRUG DEVELOPMENT RESEARCH, Issue 4 2003Takashi Nakazawa Abstract Adhesion of fibroblast-like synoviocytes (FLSs) to T cells through the interaction of lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) plays a pivotal role in the pathogenesis of rheumatoid arthritis (RA). We therefore used flow cytometry and quantitative polymerase chain reaction (PCR) to examine the effect of adenosine and its derivatives on expression of ICAM-1 induced by tumor necrosis factor-alpha and interferon-gamma in primary rheumatoid FLSs (RA-FLSs) and E11 cells, an RA-FLS line. Exposing cells to adenosine (5,500 µM) for 24 h in the presence of coformycin, an adenosine deaminase inhibitor, concentration-dependently inhibited cytokine-induced transcription of ICAM-1 mRNA, as well as subsequent surface expression of the protein. Although transcription of all four adenosine receptor isoforms has been detected in FLSs, neither the A1 receptor agonist R-PIA, the A2A receptor agonist CGS21680 nor the A3 agonist Cl-IB-MECA had any effect on cytokine-induced ICAM-1 expression. Conversely, A1/A2 receptor antagonist xanthine amine congener and A2A antagonist ZM240385 both failed to suppress the effect of adenosine. Adenosine appears to inhibit cytokine-induced ICAM-1 expression in FLSs independently of adenosine receptor-mediated signaling. By contrast, the effect of adenosine was neutralized by nitrobenzylmercaptopurin, a nucleoside transporter inhibitor, or by ABT702, an adenosine kinase inhibitor. This suggests that adenosine taken up via the nucleoside transporter is phosphorylated by adenosine kinase, and the resultant phospho-adenosine interferes with the ICAM-1 transcription and cell surface expression. Downregulation of T cell,FLS interaction by adenosine may thus represent a novel approach to the treatment of RA. Drug Dev. Res. 58:368,376, 2003. © 2003 Wiley-Liss, Inc. [source] Development of off-line and on-line capillary electrophoresis methods for the screening and characterization of adenosine kinase inhibitors and substratesELECTROPHORESIS, Issue 12 2006Jamshed Iqbal Abstract Fast and convenient CE assays were developed for the screening of adenosine kinase,(AK) inhibitors and substrates. In the first method, the enzymatic reaction was performed in a test tube and the samples were subsequently injected into the capillary by pressure and detected by their UV absorbance at 260,nm. An MEKC method using borate buffer (pH,9.5) containing 100,mM SDS (method,A) was suitable for separating alternative substrates (nucleosides). For the CE determination of AMP formed as a product of the AK reaction, a phosphate buffer (pH,7.5 or 8.5) was used and a constant current (95,,A) was applied (method,B). The methods employing a fused-silica capillary and normal polarity mode provided good resolution of substrates and products of the enzymatic reaction and a short analysis time of less than 10,min. To further optimize and miniaturize the AK assays, the enzymatic reaction was performed directly in the capillary, prior to separation and quantitation of the product employing electrophoretically mediated microanalysis (EMMA, method,C). After hydrodynamic injection of a plug of reaction buffer (20,mM Tris-HCl, 0.2,mM MgCl2, pH,7.4), followed by a plug containing the enzyme, and subsequent injection of a plug of reaction buffer containing 1,mM,ATP, 100,,M adenosine, and 20,,M,UMP as an internal standard,(I.S.), as well as various concentrations of an inhibitor, the reaction was initiated by the application of 5,kV separation voltage (negative polarity) for 0.20,min to let the plugs interpenetrate. The voltage was turned off for 5,min (zero-potential amplification) and again turned on at a constant current of ,60,,A to elute the products within 7,min. The method employing a polyacrylamide-coated capillary of 20,cm effective length and reverse polarity mode provided good resolution of substrates and products. Dose,response curves and calculated Ki values for standard antagonists obtained by CE were in excellent agreement with data obtained by the standard radioactive assay. [source] Increased tumor necrosis factor ,,converting enzyme activity induces insulin resistance and hepatosteatosis in mice,HEPATOLOGY, Issue 1 2010Loredana Fiorentino Tumor necrosis factor ,,converting enzyme (TACE, also known as ADAM17) was recently involved in the pathogenesis of insulin resistance. We observed that TACE activity was significantly higher in livers of mice fed a high-fat diet (HFD) for 1 month, and this activity was increased in liver > white adipose tissue > muscle after 5 months compared with chow control. In mouse hepatocytes, C2C12 myocytes, and 3T3F442A adipocytes, TACE activity was triggered by palmitic acid, lipolysaccharide, high glucose, and high insulin. TACE overexpression significantly impaired insulin-dependent phosphorylation of AKT, GSK3, and FoxO1 in mouse hepatocytes. To test the role of TACE activation in vivo, we used tissue inhibitor of metalloproteinase 3 (Timp3) null mice, because Timp3 is the specific inhibitor of TACE and Timp3,/, mice have higher TACE activity compared with wild-type (WT) mice. Timp3,/, mice fed a HFD for 5 months are glucose-intolerant and insulin-resistant; they showed macrovesicular steatosis and ballooning degeneration compared with WT mice, which presented only microvesicular steatosis. Shotgun proteomics analysis revealed that Timp3,/, liver showed a significant differential expression of 38 proteins, including lower levels of adenosine kinase, methionine adenosysltransferase I/III, and glycine N -methyltransferase and higher levels of liver fatty acid-binding protein 1. These changes in protein levels were also observed in hepatocytes infected with adenovirus encoding TACE. All these proteins play a role in fatty acid uptake, triglyceride synthesis, and methionine metabolism, providing a molecular explanation for the increased hepatosteatosis observed in Timp3,/, compared with WT mice. Conclusion: We have identified novel mechanisms, governed by the TACE,Timp3 interaction, involved in the determination of insulin resistance and liver steatosis during overfeeding in mice. (HEPATOLOGY 2009.) [source] 2,-Deoxyadenosine causes apoptotic cell death in a human colon carcinoma cell lineJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 6 2003Michela Giannecchini Abstract The combination of 2,-deoxyadenosine and 2,-deoxycoformycin is toxic for the human colon carcinoma cell line LoVo. In this study we investigated the mode of action of the two compounds and have found that they promote apoptosis. The examination by fluorescence microscopy of the cells treated with the combination revealed the characteristic morphology associated with apoptosis, such as chromatin condensation and nuclear fragmentation. The occurrence of apoptosis was also confirmed by the release of cytochrome c and the proteolytic processing of procaspase-3 in cells subjected to the treatment. To exert its triggering action on the apoptotic process, 2,-deoxyadenosine enters the cells through an equilibrative nitrobenzyl-thioinosine-insensitive carrier, and must be phosphorylated by intracellular kinases. Indeed, in the present work we demonstrate by analysis of the intracellular metabolic derivatives of 2,-deoxyadenosine that, as suggested by our previous findings, in the incubation performed with 2,-deoxyadenosine and 2,-deoxycoformycin, an appreciable amount of dATP was formed. Conversely, when also an inhibitor of adenosine kinase was added to the incubation mixture, dATP was not formed, and the toxic and apoptotic effect of the combination was completely reverted. © 2003 Wiley Periodicals, Inc. J Biochem Mol Toxicol 17:329,337, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10095 [source] Prenatal alcohol exposure alters phosphorylation and glycosylation of proteins in rat offspring liverPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 3 2010Bourlaye Fofana Abstract To gain more insights into the translational and PTM that occur in rat offspring exposed to alcohol in utero, 2-D PAGE with total, phospho- and glycoprotein staining and MALDI-MS/MS and database searching were conducted. The results, based on fold-change expression, revealed a down-regulation of total protein expression by prenatal alcohol exposure in 7-day-old and 3-month-old rats. There was an up-regulation of protein phosphorylation but a down-regulation of glycosylation by prenatal alcohol exposure in both age groups. Of 31 protein spots examined per group, differentially expressed proteins were identified as ferritin light chain, aldo-keto reductase, tumor rejection antigen gp96, fructose-1,6-bisphosphatase, glycerol-3-phosphate dehydrogenase, malate dehydrogenase, and ,-actin. Increased phosphorylation was observed in proteins such as calmodulin, gluthatione S-transferase, glucose regulated protein 58, ,-enolase, eukaryotic translation elongation factor 1 ,-2, riboprotein large P2, agmatinase, ornithine carbamoyltransferase, quinolinate phosphoribosyltransferase, formimidoyltransferase cyclodeaminase, and actin. In addition, glycosylation of adenosine kinase, adenosylhomocysteine hydrolase, and 3-hydroxyanthranilate dioxygenase was reduced. Pathways affected by these protein alterations include cell signaling, cellular stress, protein synthesis, cytoskeleton, as well as glucose, aminoacid, adenosine and energy metabolism. The activity of the gluconeogenic enzyme fructose-1,6-bisphosphatase was elevated by prenatal alcohol. The observations may have important physiological implications. [source] Prevalidation of potential protein biomarkers in toxicology using iTRAQÔ reagent technologyPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 10 2007Matthias Glückmann Abstract Today, toxicoproteomics still relies mainly on 2-DE followed by MS for detection and identification of proteins, which might characterize a certain state of disease, indicate toxicity or even predict carcinogenicity. We utilized the classical 2-DE/MS approach for the evaluation of early protein biomarkers which are predictive for chemically induced hepatocarcinogenesis in rats. We were able to identify statistically significantly deregulated proteins in N -nitrosomorpholine exposed rat liver tissue. Based on literature data, biological relevance in the early molecular process of hepatocarcinogenicity could be suggested for most of these potential biomarkers. However, in order to ensure reliable results and to create the prerequisites necessary for integration in routine toxicology studies in the future, these protein expression patterns need to be prevalidated using independent technology platforms. In the current study, we evaluated the usefulness of iTRAQÔ reagent technology (Applied Biosystems, Framingham, USA), a recently introduced MS-based protein quantitation method, for verification of the 2-DE/MS biomarkers. In summary, the regulation of 26 2-DE/MS derived protein biomarkers could be verified. Proteins like HSP 90-beta, annexin A5, ketohexokinase, N -hydroxyarylamine sulfotransferase, ornithine aminotransferase, and adenosine kinase showed highly comparable fold changes using both proteomic quantitation strategies. In addition, iTRAQ analysis delivered further potential biomarkers with biological relevance to the processes of hepatocarcinogenicity: e.g. placental form of glutathione S-transferase (GST-P), carbonic anhydrase, and aflatoxin B1 aldehyde reductase. Our results show both the usefulness of iTRAQ reagent technology for biomarker prevalidation as well as for identification of further potential marker proteins, which are indicative for liver hepatocarcinogenicity. [source] Substrate analogs induce an intermediate conformational change in Toxoplasma gondii adenosine kinaseACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2007Yan Zhang Adenosine kinase (AK) is a key enzyme in purine metabolism in the ubiquitous intracellular parasite Toxoplasma gondii and is a potential chemotherapeutic target for the treatment of T. gondii infections. To better understand the structure,activity relationship of 6-substituted purine ribosides, the structures of the T. gondii AK,N6,N6 -dimethyladenosine (DMA) complex, the AK,DMA,AMP-PCP complex, the AK,6-methyl mercaptopurine riboside (MMPR) complex and the AK,MMPR,AMP-PCP complex were determined to 1.35, 1.35, 1.75 and 1.75,Å resolution, respectively. These structures reveal a conformation intermediate between open and closed, with a small lid-domain rotation of 12°. Residues Gly143- X - X -Gly146 undergo torsional changes upon substrate binding, which together with a Gly68-Gly69 switch induces a hinge bending of the lid domain. The intermediate conformation suggests that ATP binding is independent of adenosine binding. Orienting the ,-phosphate group of ATP into the optimal catalytic position may be the last step before the onset of chemical catalysis and may require the translocation of Arg136 following the complete closure of the lid domain. 6-Substituted purine-nucleoside analogs are accommodated in a hydrophobic cavity. Modification at the N6 or C6 position of the nucleoside would affect the interactions with the surrounding residues and the binding affinity. [source] Adenosine modulates cell growth in baby hamster kidney (BHK) cellsBIOFACTORS, Issue 4 2000Rashmi A. Mittal Abstract Adenosine is known to modulate cell growth in a variety of mammalian cells either via the activation of receptors or through metabolism. We investigated the effect of adenosine on Baby Hamster Kidney (BHK) cell growth and attempted to determine its mechanism of modulation. In wild-type BHK cells, adenosine evoked a biphasic response in which a low concentration of adenosine (1± 150;5 ,M) produced an inhibition of colony formation but at higher concentrations (up to 50 ,M) this inhibition was progressively reversed. However, no biphasic response was observed in an ± 147;adenosine kinase± 148; deficient BHK mutant, ± 147;5a± 148;, which suggests that adenosine kinase plays an important role in the modulation of growth response to adenosine. Adenosine receptors did not appear to have a role in regulating cell growth of BHK cells. Specific A1 and A2 receptor antagonists were unable to reverse the effect of adenosine on cell growth. Even though a specific A3 adenosine receptor antagonist MRS-1220 partly reversed the inhibition in colony formation at 1 ,M adenosine, it also affected the transport of adenosine. Thus adenosine transport and metabolism appears to play the major role in this modulation of cell growth as 5,-amino-5,-deoxyadenosine, an adenosine kinase inhibitor, reversed the inhibition of cell growth observed at 1 ,M adenosine. These results, taken together, would suggest that adenosine modulates cell growth in BHK mainly through its transport and metabolism to adenine nucleotides. [source] Searching Inhibitors of Adenosine Kinase by Simulation MethodsCHINESE JOURNAL OF CHEMISTRY, Issue 11 2006Rui-Xin Zhu Abstract Searching new inhibitors of adenosine kinase (AK) is still drawing attention of experimental scientists. A better and solid model is here proposed by means of simulation methods from different ways, the direct analysis of receptor itself, the conventional 3D-QSAR methods and the integration of docking method and the conventional QSAR analysis. [source] | ||||||||||||||||