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European Journal of Biochemistry 1980The syn in equilibrium anti equilibrium conformation about the glycosidic bond of purine nucleosides and 5'-nucleotides in different solvent systems has been...
The syn in equilibrium anti equilibrium conformation about the glycosidic bond of purine nucleosides and 5'-nucleotides in different solvent systems has been investigated by means of 1H NMR spectroscopy. Quantitative values for the conformer populations were improved, relative to previous results, by a detailed study of, and a resultant derived correction for, the influence of the sugar exocyclic group conformation on the chemical shifts of the sugar ring protons. This was achieved with the aid of nucleosides and nucleotides fixed in the conformations gauche-trans [derivatives of 8,5'-(R)-cyclo] and trans-gauche [derivatives of 8,5'-(S)-cyclo]. The results of 13C NMR confirmed those obtained by 1H NMR. The measured values of the vicinal coupling constants between H-1' and the C-8 and C-4 carbons were employed to evaluate approximately the glycosidic angles chi of the nucleosides in the conformations syn and anti. A critical examination is made of the applicability of relaxation methods, involving analysis of spin-lattice relaxation time of protons (T1) and the Overhauser effect, to determine the conformation of the base about the glycosidic bond; interpretations are provided for the lack of agreement between these methods and those based on chemical shifts in the present study. The foregoing resuls are also applied to an examination of the effect of the conformation of the base about the glycosidic bond on the enzymatic reactions catalyzed by 5'-nucleotidase and adenosine deaminase.
Topics: Adenosine; Chemical Phenomena; Chemistry; Guanosine; Isomerism; Magnetic Resonance Spectroscopy; Motion; Purine Nucleosides; Purine Nucleotides; Structure-Activity Relationship
PubMed: 7408842
DOI: 10.1111/j.1432-1033.1980.tb04701.x -
British Journal of Pharmacology Jun 2003(1) Here, we investigated how nucleotides and nucleosides affect the release of tritiated purines and endogenous adenosine 5'-triphosphate (ATP) from superfused rat...
(1) Here, we investigated how nucleotides and nucleosides affect the release of tritiated purines and endogenous adenosine 5'-triphosphate (ATP) from superfused rat hippocampal slices. (2) ATP elicited concentration-dependent [(3)H]purine efflux from slices preloaded with [(3)H]adenosine. High-performance liquid chromatography analysis of the effluent showed that the tritium label represented the whole set of adenine nucleotides and nucleosides, and ATP significantly increased the outflow of [(3)H]ATP. (3) Adenosine 5'-diphosphate, adenosine, uridine, uridine 5'-triphosphate, alpha,beta-methylene-ATP and 3'-O-(4-benzoylbenzoyl)-ATP were also active in eliciting [(3)H]purine release. Adenosine (300 micro M) also evoked endogenous ATP efflux from the hippocampal slices. (4) Reverse transcription-coupled-polymerase chain reaction analysis revealed that mRNAs encoding a variety of P2X and P2Y receptor proteins are expressed in the rat hippocampus. Nevertheless, neither P2 receptor (i.e. pyridoxal-5-phosphate-6-azophenyl-2',4'-disulphonic acid, 30 micro M, suramin, 300 micro M and reactive blue 2, 10 micro M), nor adenosine receptor (8-cyclopentyl-1,3-dipropylxanthine, 250 nM and dimethyl-1-propargylxanthine, 250 nM) antagonists modified the effect of ATP (300 micro M) to evoke [(3)H]purine release. (5) The nucleoside transport inhibitors, dipyridamole (10 micro M), nitrobenzylthioinosine (10 micro M) and adenosine deaminase (2-10 U ml(-1)), but not the ecto-adenylate kinase inhibitor diadenosine pentaphosphate (200 micro M) significantly reduced ATP-evoked [(3)H]purine efflux. (6) In summary, we found that ATP and other nucleotides and nucleosides promote the release of one another and themselves by the nucleoside transport system. This action could have relevance during physiological and pathological elevation of extracellular purine levels high enough to reverse the nucleoside transporter.
Topics: Adenine Nucleotides; Adenosine Triphosphate; Animals; Hippocampus; In Vitro Techniques; Male; Protein Transport; Purine Nucleosides; Purines; Rats; Rats, Wistar
PubMed: 12788822
DOI: 10.1038/sj.bjp.0705285 -
Biochemistry Apr 2023Adenosine deaminases acting on RNA (ADARs) are RNA editing enzymes that catalyze the hydrolytic deamination of adenosine (A) to inosine (I) in dsRNA. In humans, two...
Adenosine deaminases acting on RNA (ADARs) are RNA editing enzymes that catalyze the hydrolytic deamination of adenosine (A) to inosine (I) in dsRNA. In humans, two catalytically active ADARs, ADAR1 and ADAR2, perform this A-to-I editing event. The growing field of nucleotide base editing has highlighted ADARs as promising therapeutic agents while multiple studies have also identified ADAR1's role in cancer progression. However, the potential for site-directed RNA editing as well as the rational design of inhibitors is being hindered by the lack of detailed molecular understanding of RNA recognition by ADAR1. Here, we designed short RNA duplexes containing the nucleoside analog, 8-azanebularine (8-azaN), to gain insight into molecular recognition by the human ADAR1 catalytic domain. From gel shift and in vitro deamination experiments, we validate ADAR1 catalytic domain's duplex secondary structure requirement and present a minimum duplex length for binding (14 bp, with 5 bp 5' and 8 bp 3' to editing site). These findings concur with predicted RNA-binding contacts from a previous structural model of the ADAR1 catalytic domain. Finally, we establish that neither 8-azaN as a free nucleoside nor a ssRNA bearing 8-azaN inhibits ADAR1 and demonstrate that the 8-azaN-modified RNA duplexes selectively inhibit ADAR1 and not the closely related ADAR2 enzyme.
Topics: Humans; Ribonucleosides; Purine Nucleosides; RNA, Double-Stranded; Adenosine; Adenosine Deaminase
PubMed: 36972568
DOI: 10.1021/acs.biochem.2c00686 -
The Journal of Biological Chemistry May 1992The overall goal of this study was to determine the mechanisms by which nucleosides are transported in choroid plexus. Choroid plexus tissue slices obtained from rabbit...
The overall goal of this study was to determine the mechanisms by which nucleosides are transported in choroid plexus. Choroid plexus tissue slices obtained from rabbit brain were depleted of ATP with 2,4-dinitrophenol. Uridine and thymidine accumulated in the slices against a concentration gradient in the presence of an inwardly directed Na+ gradient. The Na(+)-driven uptake of uridine and thymidine was saturable with Km values of 18.1 +/- 2.0 and 13.0 +/- 2.3 microM and Vmax values of 5.5 +/- 0.3 and 1.0 +/- 0.2 nmol/g/s, respectively. Na(+)-driven uridine uptake was inhibited by naturally occurring ribo- and deoxyribonucleosides (adenosine, cytidine, and thymidine) but not by synthetic nucleoside analogs (dideoxyadenosine, dideoxycytidine, cytidine arabinoside, and 3'-azidothymidine). Both purine (guanosine, inosine, formycin B) and pyrimidine nucleosides (uridine and cytidine) were potent inhibitors of Na(+)-thymidine transport with IC50 values ranging between 5 and 23 microM. Formycin B competitively inhibited Na(+)-thymidine uptake and thymidine trans-stimulated formycin B uptake. These data suggest that both purine and pyrimidine nucleosides are substrates of the same system. The stoichiometric coupling ratios between Na+ and the nucleosides, guanosine, uridine, and thymidine, were 1.87 +/- 0.10, 1.99 +/- 0.35, and 2.07 +/- 0.09, respectively. The system differs from Na(+)-nucleoside co-transport systems in other tissues which are generally selective for either purine or pyrimidine nucleosides and which have stoichiometric ratios of 1. This study represents the first direct demonstration of a unique Na(+)-nucleoside co-transport system in choroid plexus.
Topics: Adenosine Triphosphate; Animals; Carrier Proteins; Choroid Plexus; Cytarabine; Didanosine; Membrane Proteins; Nucleoside Transport Proteins; Purine Nucleosides; Pyrimidine Nucleosides; Rabbits; Sodium; Substrate Specificity; Zalcitabine; Zidovudine
PubMed: 1315741
DOI: No ID Found -
The Journal of Physiology Aug 19931. The absorption and metabolism of purine nucleosides and their constituent bases has been investigated by perfusion through the lumen of isolated loops of rat jejunum....
1. The absorption and metabolism of purine nucleosides and their constituent bases has been investigated by perfusion through the lumen of isolated loops of rat jejunum. In control perfusions and those with luminal purines or purine nucleosides, high-performance liquid chromatography (HPLC) revealed uric acid as the only detectable purine in the mucosal epithelial layer and the serosal secretions unless the xanthine oxidase inhibitor allopurinol was present. 2. Adenosine (0.5 mM) was quantitatively deaminated to inosine in the lumen after perfusion for 30 min. 3. Luminal inosine and hypoxanthine (0.15-1.0 mM) increased the serosal uric acid concentration significantly (P < 0.001); at 0.5 and 1.0 mM the nucleoside gave a significantly greater (P < 0.01) rate of serosal uric acid appearance than the base. 4. Luminal guanosine (0.05-0.50 mM) and guanine (0.05-0.15 mM) increased the serosal uric acid concentration significantly (P < 0.001); with 0.15 mM nucleoside the serosal uric acid appeared significantly faster (P < 0.01) than it did from the base. 5. Luminal allopurinol (0.3 mM) inhibited xanthine oxidase by 80% and reduced serosal purine appearance significantly (P < 0.01) from luminal guanine, hypoxanthine and inosine. With allopurinol, guanosine (0.1 and 0.15 mM) and inosine (0.1-1.0 mM) gave significantly higher (P < 0.01) total serosal purine concentrations than their respective bases. 6. Inosine and guanosine were cleaved to their respective bases plus ribose phosphate by the action of a cytoplasmic nucleoside phosphorylase, which was found to have widely different Michaelis constants (Km; 318 +/- 45 and 41.4 +/- 3.6 microM for inosine and guanosine, respectively) and maximum velocities (Vmax; 79.3 +/- 4.0 and 20.5 +/- 0.05 mumol min-1 (mg protein)-1 for inosine and guanosine, respectively). 7. We conclude that hypoxanthine and guanine absorbed by rat small intestine are oxidized to uric acid which is released in the serosa. The corresponding nucleosides are split by phosphorolysis after absorption and the resulting purine bases are converted to uric acid which appears on the serosal side with similar quantities of ribose phosphate.
Topics: Allopurinol; Animals; Biological Transport, Active; Chromatography, High Pressure Liquid; In Vitro Techniques; Intestinal Absorption; Intestinal Mucosa; Jejunum; Male; Purine Nucleosides; Purine-Nucleoside Phosphorylase; Purines; Pyrimidines; Rats; Rats, Wistar; Xanthine Oxidase
PubMed: 8254512
DOI: 10.1113/jphysiol.1993.sp019773 -
Antiviral Chemistry & Chemotherapy May 2000A series of R and S enantiomers of 2-aminopurine methylenecyclopropane analogues of nucleosides was synthesized. Two diastereoisomeric lipophilic phosphate prodrugs...
Synthesis and enantioselectivity of the antiviral effects of (R,Z)-,(S,Z)-methylenecyclopropane analogues of purine nucleosides and phosphoralaninate prodrugs: influence of heterocyclic base, type of virus and host cells.
A series of R and S enantiomers of 2-aminopurine methylenecyclopropane analogues of nucleosides was synthesized. Two diastereoisomeric lipophilic phosphate prodrugs derived from R and S enantiomers of 2,6-diaminopurine analogue were also prepared. Enantioselectivity (diastereoselectivity in case of prodrugs) of in vitro antiviral effects was investigated with human and murine cytomegalovirus (HCMV and MCMV, respectively), herpes simplex virus types 1 and 2 (HSV-1 and HSV-2, respectively), human immunodeficiency virus type 1 (HIV-1), hepatitis B virus (HBV), Epstein-Barr virus (EBV) and varicella zoster virus (VZV). Strong differences in enantioselectivity were found between the R and S enantiomers of adenine analogue and enantiomeric 2-aminopurine analogues. Thus, the enantiomers of adenine analogue were equipotent against HCMV but not MCMV, where the S enantiomer is strongly preferred. The same S preference was found throughout the 2-aminopurine series for both HCMV and MCMV. In contrast, R-synadenol in HIV-1 assays was the best agent, whereas the S enantiomers of moderately effective 2-amino-6-cyclopropylamino and 2-amino-6-methoxypurine analogues were preferred. Little enantiomeric preference was found for R and S enantiomers of synadenol and the corresponding enantiomers of 2,6-diaminopurine analogue against HBV. A mixed pattern of enantioselectivity was observed for EBV depending on the type of host cells and assay. Against VZV, the R and S enantiomers of adenine analogue were equipotent or almost equipotent, but throughout the series of 2-aminopurine analogues a distinct preference for the S enantiomers was found. The stereoselectivity pattern of both diastereoisomeric prodrugs mostly followed enantioselectivity of the parent analogues. The varying enantioselectivities in the series of purine methylenecyclopropane analogues are probably a consequence of differences in the mechanisms of action in different virus/host cell systems.
Topics: Adenosine; Alanine; Animals; Antiviral Agents; Chromatography, High Pressure Liquid; Cyclopropanes; Cytomegalovirus; HIV-1; Hepatitis B virus; Herpesviridae; Herpesvirus 3, Human; Herpesvirus 4, Human; Humans; Molecular Structure; Prodrugs; Stereoisomerism; Virus Replication; Viruses
PubMed: 10901290
DOI: 10.1177/095632020001100302 -
International Journal of Molecular... May 2019Effects of fructose 1,6-bisphosphate (F-1,6-P2) towards -methyl-d-aspartate NMDA excitotoxicity were evaluated in rat organotypic hippocampal brain slice cultures (OHSC)...
Effects of fructose 1,6-bisphosphate (F-1,6-P2) towards -methyl-d-aspartate NMDA excitotoxicity were evaluated in rat organotypic hippocampal brain slice cultures (OHSC) challenged for 3 h with 30 μM NMDA, followed by incubations (24, 48, and 72 h) without (controls) and with F-1,6-P2 (0.5, 1 or 1.5 mM). At each time, cell necrosis was determined by measuring LDH in the medium. Energy metabolism was evaluated by measuring ATP, GTP, ADP, AMP, and ATP catabolites (nucleosides and oxypurines) in deproteinized OHSC extracts. Gene expressions of phosphofructokinase, aldolase, and glyceraldehyde-3-phosphate dehydrogenase were also measured. F-1,6-P2 dose-dependently decreased NMDA excitotoxicity, abolishing cell necrosis at the highest concentration tested (1.5 mM). Additionally, F-1,6-P2 attenuated cell energy imbalance caused by NMDA, ameliorating the mitochondrial phosphorylating capacity (increase in ATP/ADP ratio) Metabolism normalization occurred when using 1.5 mM F-1,6-P2. Remarkable increase in expressions of phosphofructokinase, aldolase and glyceraldehyde-3-phosphate dehydrogenase (up to 25 times over the values of controls) was also observed. Since this phenomenon was recorded even in OHSC treated with F-1,6-P2 with no prior challenge with NMDA, it is highly conceivable that F-1,6-P2 can enter into intact cerebral cells producing significant benefits on energy metabolism. These effects are possibly mediated by changes occurring at the gene level, thus opening new perspectives for F-1,6-P2 application as a useful adjuvant to rescue mitochondrial metabolism of cerebral cells under stressing conditions.
Topics: Animals; Energy Metabolism; Fructose-Bisphosphatase; Fructose-Bisphosphate Aldolase; Glyceraldehyde-3-Phosphate Dehydrogenases; Hippocampus; N-Methylaspartate; Necrosis; Neuroprotective Agents; Phosphofructokinases; Purine Nucleosides; Rats; Rats, Wistar
PubMed: 31067671
DOI: 10.3390/ijms20092239 -
The Oncologist Jan 2006Chronic lymphocytic leukemia (CLL) is a low-grade B-lineage lymphoid malignancy but may have more heterogeneity than previously thought. Many cases require no treatment... (Review)
Review
Chronic lymphocytic leukemia (CLL) is a low-grade B-lineage lymphoid malignancy but may have more heterogeneity than previously thought. Many cases require no treatment at all because of an indolent course, while other patients become symptomatic or develop signs of rapid progression. Treatment is usually noncurative and is directed at reducing the symptoms. Some molecular risk features may help delineate, at initial diagnosis, which patients will have a more aggressive course. Newer CLL treatment regimens incorporating purine nucleoside analogues and monoclonal antibodies have increased the rate of molecular complete remissions, which may lead to better survival times. Reduced intensity allogeneic transplant conditioning regimens have made the potentially curative modality more widely available. All these treatments have significant risks for infectious complications, which must be carefully weighed against the risks posed by the underlying disease. A proposed risk-based treatment algorithm is discussed.
Topics: Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Biomarkers, Tumor; Hematopoietic Stem Cell Transplantation; Humans; Immunotherapy; Leukemia, Lymphocytic, Chronic, B-Cell; Neoplasm Staging; Purine Nucleosides
PubMed: 16401710
DOI: 10.1634/theoncologist.11-1-21 -
The Biochemical Journal Mar 1987Deoxyadenosine (dAdo) and deoxyguanosine (dGuo) decrease methionine synthesis from homocysteine in cultured lymphoblasts; because of the possible trapping of...
Deoxyadenosine (dAdo) and deoxyguanosine (dGuo) decrease methionine synthesis from homocysteine in cultured lymphoblasts; because of the possible trapping of 5-methyltetrahydrofolate this could lead to decreased purine nucleotide synthesis. Since purine deoxynucleosides could also inhibit purine synthesis de novo at an early step not involving folate metabolism, we measured in azaserine-treated cells 5-amino-4-imidazolecarboxamide (Z-base)-dependent purine nucleotide synthesis using [14C]formate. In the T lymphoblasts, Z-base-dependent purine nucleotide synthesis was decreased 26% by 0.3 microM-dAdo, 21% by 1 microM-dGuo and 28% by 1 microM-adenosine dialdehyde, a potent S-adenosylhomocysteine hydrolase inhibitor; homocysteine fully reversed the inhibitions. The B lymphoblasts were considerably less sensitive to the deoxynucleoside-induced decrease in Z-base-dependent purine nucleotide synthesis, with 100 microM-dAdo required for significant inhibition and no inhibition by dGuo at this concentration; homocysteine partly reversed the inhibition by dAdo. The observed decrease in Z-base-dependent purine nucleotide synthesis could not be attributed either to dUMP depletion changing the folate pools or to decreased ATP availability because dUrd was without effect and during the experimental period the intracellular ATP concentration did not change significantly. Cells with 5,10-methylenetetrahydrofolate reductase deficiency were relatively resistant to inhibition of Z-base-dependent purine nucleotide synthesis by dAdo and adenosine dialdehyde. Our results suggest that deoxynucleosides decrease purine nucleotide synthesis by trapping 5-methyltetrahydrofolate.
Topics: 5,10-Methylenetetrahydrofolate Reductase (FADH2); Adenosine; Adenosine Deaminase; Aminoimidazole Carboxamide; B-Lymphocytes; Cell Line; Folic Acid; Humans; Imidazoles; Methylenetetrahydrofolate Reductase (NADPH2); Oxidoreductases; Purine Nucleosides; Purine Nucleotides; Purine-Nucleoside Phosphorylase; Purines; T-Lymphocytes
PubMed: 3109390
DOI: 10.1042/bj2420425 -
Clinical Pharmacokinetics Aug 2016The 2014-2015 outbreak of Ebola virus disease is the largest epidemic to date in terms of the number of cases, deaths, and affected areas. In October 2015, no antiviral... (Review)
Review
The 2014-2015 outbreak of Ebola virus disease is the largest epidemic to date in terms of the number of cases, deaths, and affected areas. In October 2015, no antiviral agents had proven antiviral efficacy in patients. However, in September 2014, the World Health Organization inventoried and has since regularly updated a list of potential drug candidates with demonstrated antiviral efficacy in in vitro or animal models. This includes agents belonging to various therapeutic classes, namely direct antiviral agents (favipiravir and BCX4430), a combination of antibodies (ZMapp), type I interferons, RNA interference-based drugs (TKM-Ebola and AVI-7537), and anticoagulant drugs (rNAPc2). Here, we review the pharmacokinetic and pharmacodynamic information presently available for these drugs, using data obtained in healthy volunteers for pharmacokinetics and data obtained in human clinical trials or animal models for pharmacodynamics. Future studies evaluating these drugs in clinical trials are critical to confirm their efficacy in humans, propose appropriate doses, and evaluate the possibility of treatment combinations.
Topics: Adenine; Adenosine; Amides; Animals; Antiviral Agents; Disease Outbreaks; Ebolavirus; Healthy Volunteers; Hemorrhagic Fever, Ebola; Humans; Models, Animal; Purine Nucleosides; Pyrazines; Pyrrolidines
PubMed: 26798032
DOI: 10.1007/s40262-015-0364-1