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Annals of Oncology : Official Journal... 1996The observation of lymphopenia in children deficient in adenosine deaminase (ADA) led to exploration of an inhibitor of the enzyme in lymphoid malignancies; thus... (Review)
Review
The observation of lymphopenia in children deficient in adenosine deaminase (ADA) led to exploration of an inhibitor of the enzyme in lymphoid malignancies; thus deoxycoformycin was the first purine nucleotide used in human trials. Fludarabine and 2-chlorodeoxyadenosine (2-CdA), agents resistant to deamination by ADA, have been utilized in the past decade. All of these drugs act as competitors for deoxyadenosine triphosphate at the A sites of the elongating DNA strand, terminating DNA synthesis. However, their remarkable efficacy in indolent lymphoid malignancies is not well explained by this mechanism of action. The induction of apoptosis and resultant cytotoxicity may be important in their activity. As a single agent, fludarabine has been associated with overall remission rates as high as 55% in previously treated patients and 79% in previously untreated patients. With this agent, a dosage regimen of 25-30 mg/m2 daily over 5 days seems to be the most effective to date. Fludarabine has shown more favorable remission rates than the traditional salvage regimens incorporating anthracyclines and alkylating agents. Regimens combining fludarabine with mitoxantrone and with doxorubicin have shown minimal therapeutic advantage in CLL, while combination with cyclophosphamide appears promising. Remission rates with deoxycoformycin have been lower than with fludarabine, but studies have been small in patient numbers. The agent 2-CdA, first successful in hairy-cell leukemia, has shown overall response rates in chronic lymphocytic leukemia similar to those seen with fludarabine. Whether or not cross-resistance occurs among the purine analogs has not been fully determined, but occasional patients with disease refractory to fludarabine have responded to 2-CdA. Cumulative myelosuppression and immunosuppression may be experienced however. In the B-cell neoplastic entity, Waldenström's macroglobulinemia, fludarabine therapy in patients previously treated with alkylating agents and/or steroids produced a 36% response rate. Only two previously untreated patients received fludarabine, and both responded. A similar response rate of 40% was seen when 2-CdA was administered to previously treated patients. This response rate increased to 85% in a study of 26 previously untreated patients, making this one of the most effective drugs yet investigated in this condition.
Topics: Antineoplastic Agents; Cladribine; Clinical Trials as Topic; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Purine Nucleosides; Vidarabine; Waldenstrom Macroglobulinemia
PubMed: 9010576
DOI: 10.1093/annonc/7.suppl_6.s27 -
Journal of Visualized Experiments : JoVE Apr 2013The involvement of free radicals in life sciences has constantly increased with time and has been connected to several physiological and pathological processes. This...
The involvement of free radicals in life sciences has constantly increased with time and has been connected to several physiological and pathological processes. This subject embraces diverse scientific areas, spanning from physical, biological and bioorganic chemistry to biology and medicine, with applications to the amelioration of quality of life, health and aging. Multidisciplinary skills are required for the full investigation of the many facets of radical processes in the biological environment and chemical knowledge plays a crucial role in unveiling basic processes and mechanisms. We developed a chemical biology approach able to connect free radical chemical reactivity with biological processes, providing information on the mechanistic pathways and products. The core of this approach is the design of biomimetic models to study biomolecule behavior (lipids, nucleic acids and proteins) in aqueous systems, obtaining insights of the reaction pathways as well as building up molecular libraries of the free radical reaction products. This context can be successfully used for biomarker discovery and examples are provided with two classes of compounds: mono-trans isomers of cholesteryl esters, which are synthesized and used as references for detection in human plasma, and purine 5',8-cyclo-2'-deoxyribonucleosides, prepared and used as reference in the protocol for detection of such lesions in DNA samples, after ionizing radiations or obtained from different health conditions.
Topics: Biomarkers; Biomimetic Materials; Cholesterol Esters; Free Radicals; Humans; Purine Nucleosides
PubMed: 23629513
DOI: 10.3791/50379 -
The Biochemical Journal Sep 1997A purine nucleoside- and nucleotide-binding protein has been isolated from extracts of rat and rabbit heart, calf aortic smooth muscle and rat liver using an affinity...
A purine nucleoside- and nucleotide-binding protein has been isolated from extracts of rat and rabbit heart, calf aortic smooth muscle and rat liver using an affinity column containing adenosine bound through the N6-position. The protein, which was eluted by adenosine, was cloned and expressed in Escherichia coli. The deduced amino acid sequence has a calculated Mr of 13693 (p13.7). The expressed protein has properties identical with the protein isolated from heart and liver, including an anomalous, apparent Mr of 15300, observed on gel electrophoresis. Gel filtration shows it to be a dimer. p13.7 differs by only three amino acids out of 125 from protein kinase C inhibitor 1 [Pearson, DeWald, Mathews, Mozier, Zürcher-Neely, Heinrikson, Morris, McCubbin, McDonald, Fraser et al. (1990) J. Biol. Chem. 265, 4583-4591]. However, we have not been able to demonstrate inhibition of protein kinase C by physiological concentrations of p13.7, regardless of whether it was isolated from tissue extracts or expressed in E. coli. p13.7 is a member of the histidine triad motif family of proteins [Séraphin (1992) J. DNA Sequencing Mapping 3, 177-179]. The affinity of p13.7 for a number of different purine nucleosides and nucleotides, as measured by fluorescence titration and gel filtration, falls within the range 5-50 microM. On the basis of these properties and its crystal structure [Brenner, Garrison, Gilmour, Peisach, Ringe, Petsko and Lowenstein (1997) Nature Struct. Biol. 4, 231-238], we have coined the acronym HINT (histidine triad nucleotide-binding motif) to describe the family of proteins of which p13.7 is a member. Other proteins that bind to the affinity column have been identified as malate and lactate dehydrogenases, cAMP-binding proteins, adenosine kinase and S-adenosylhomocysteine hydrolase.
Topics: Adenosine; Amino Acid Sequence; Animals; Base Sequence; Chromatography, Affinity; Cloning, Molecular; Hydrolases; Molecular Sequence Data; Molecular Weight; Organ Specificity; Protein Binding; Proteins; Purine Nucleosides; Purine Nucleotides; Rabbits; Rats; Spectrometry, Fluorescence; Titrimetry
PubMed: 9291120
DOI: 10.1042/bj3260471 -
Journal of Medicinal Chemistry Jun 2000Adenosine receptor agonists have cardioprotective, cerebroprotective, and antiinflammatory properties. We report that a carbocyclic modification of the ribose moiety...
Adenosine receptor agonists have cardioprotective, cerebroprotective, and antiinflammatory properties. We report that a carbocyclic modification of the ribose moiety incorporating ring constraints is a general approach for the design of A(1) and A(3) receptor agonists having favorable pharmacodynamic properties. While simple carbocyclic substitution of adenosine agonists greatly diminishes potency, methanocarba-adenosine analogues have now defined the role of sugar puckering in stabilizing the active adenosine receptor-bound conformation and thereby have allowed identification of a favored isomer. In such analogues a fused cyclopropane moiety constrains the pseudosugar ring of the nucleoside to either a Northern (N) or Southern (S) conformation, as defined in the pseudorotational cycle. In binding assays at A(1), A(2A), and A(3) receptors, (N)-methanocarba-adenosine was of higher affinity than the (S)-analogue, particularly at the human A(3) receptor (N/S affinity ratio of 150). (N)-Methanocarba analogues of various N(6)-substituted adenosine derivatives, including cyclopentyl and 3-iodobenzyl, in which the parent compounds are potent agonists at either A(1) or A(3) receptors, respectively, were synthesized. The N(6)-cyclopentyl derivatives were A(1) receptor-selective and maintained high efficacy at recombinant human but not rat brain A(1) receptors, as indicated by stimulation of binding of [(35)S]GTP-gamma-S. The (N)-methanocarba-N(6)-(3-iodobenzyl)adenosine and its 2-chloro derivative had K(i) values of 4.1 and 2.2 nM at A(3) receptors, respectively, and were highly selective partial agonists. Partial agonism combined with high functional potency at A(3) receptors (EC(50) < 1 nM) may produce tissue selectivity. In conclusion, as for P2Y(1) receptors, at least three adenosine receptors favor the ribose (N)-conformation.
Topics: Animals; CHO Cells; Cell Membrane; Cricetinae; Guanosine 5'-O-(3-Thiotriphosphate); Humans; Purine Nucleosides; Purinergic P1 Receptor Agonists; Radioligand Assay; Rats; Sulfur Radioisotopes
PubMed: 10841798
DOI: 10.1021/jm9905965 -
The Plant Cell Jan 2023In nucleotide metabolism, nucleoside kinases recycle nucleosides into nucleotides-a process called nucleoside salvage. Nucleoside kinases for adenosine, uridine, and...
In nucleotide metabolism, nucleoside kinases recycle nucleosides into nucleotides-a process called nucleoside salvage. Nucleoside kinases for adenosine, uridine, and cytidine have been characterized from many organisms, but kinases for inosine and guanosine salvage are not yet known in eukaryotes and only a few such enzymes have been described from bacteria. Here we identified Arabidopsis thaliana PLASTID NUCLEOSIDE KINASE 1 (PNK1), an enzyme highly conserved in plants and green algae belonging to the Phosphofructokinase B family. We demonstrate that PNK1 from A. thaliana is located in plastids and catalyzes the phosphorylation of inosine, 5-aminoimidazole-4-carboxamide-1-β-d-ribose (AICA ribonucleoside), and uridine but not guanosine in vitro, and is involved in inosine salvage in vivo. PNK1 mutation leads to increased flux into purine nucleotide catabolism and, especially in the context of defective uridine degradation, to over-accumulation of uridine and UTP as well as growth depression. The data suggest that PNK1 is involved in feedback regulation of purine nucleotide biosynthesis and possibly also pyrimidine nucleotide biosynthesis. We additionally report that cold stress leads to accumulation of purine nucleotides, probably by inducing nucleotide biosynthesis, but that this adjustment of nucleotide homeostasis to environmental conditions is not controlled by PNK1.
Topics: Inosine; Nucleosides; Nucleotides; Purine Nucleotides; Uridine
PubMed: 36342213
DOI: 10.1093/plcell/koac320 -
Proceedings of the National Academy of... Jan 2018Aqueous microdroplets (<1.3 µm in diameter on average) containing 15 mM d-ribose, 15 mM phosphoric acid, and 5 mM of a nucleobase (uracil, adenine, cytosine, or...
Aqueous microdroplets (<1.3 µm in diameter on average) containing 15 mM d-ribose, 15 mM phosphoric acid, and 5 mM of a nucleobase (uracil, adenine, cytosine, or hypoxanthine) are electrosprayed from a capillary at +5 kV into a mass spectrometer at room temperature and 1 atm pressure with 3 mM divalent magnesium ion (Mg) as a catalyst. Mass spectra show the formation of ribonucleosides that comprise a four-letter alphabet of RNA with a yield of 2.5% of uridine (U), 2.5% of adenosine (A), 0.7% of cytidine (C), and 1.7% of inosine (I) during the flight time of ∼50 µs. In the case of uridine, no catalyst is required. An aqueous solution containing guanine cannot be generated under the same conditions given the extreme insolubility of guanine in water. However, inosine can base pair with cytidine and thus substitute for guanosine. Thus, a full set of ribonucleosides to generate the purine-pyrimidine base pairs A-U and I-C are spontaneously generated in aqueous microdroplets under similar mild conditions.
Topics: Purine Nucleosides; Pyrimidine Nucleosides
PubMed: 29255025
DOI: 10.1073/pnas.1718559115 -
European Journal of Medicinal Chemistry Jan 2012A series of C-6 alkyl, cycloalkyl, and aryl-9-(β-d-ribofuranosyl)purines were synthesized and their substrate activities with Escherichia coli purine nucleoside...
Synthesis and evaluation of the substrate activity of C-6 substituted purine ribosides with E. coli purine nucleoside phosphorylase: palladium mediated cross-coupling of organozinc halides with 6-chloropurine nucleosides.
A series of C-6 alkyl, cycloalkyl, and aryl-9-(β-d-ribofuranosyl)purines were synthesized and their substrate activities with Escherichia coli purine nucleoside phosphorylase (E. coli PNP) were evaluated. (Ph(3)P)(4)Pd-mediated cross-coupling reactions of 6-chloro-9-(2,3,5-tri-O-acetyl-β-d-ribofuranosyl)-purine (6) with primary alkyl (Me, Et, n-Pr, n-Bu, isoBu) zinc halides followed by treatment with NH(3)/MeOH gave the corresponding 6-alkyl-9-(β-d-ribofuranosyl)purine derivatives 7-11, respectively, in good yields. Reactions of 6 with cycloalkyl(propyl, butyl, pentyl)zinc halides and aryl (phenyl, 2-thienyl)zinc halides gave under similar conditions the corresponding 6-cyclopropyl, cyclobutyl, cyclopentyl, phenyl, and thienyl -9-(β-d-ribofuranosyl)purine derivatives 12-16, respectively in high yields. E. coli PNP showed a high tolerance to the steric and hydrophobic environment at the 6-position of the synthesized purine ribonucleosides. Significant cytotoxic activity was observed for 8, 12, 15, and 16. Evaluation of 12 and 16 against human tumor xenografts in mice did not demonstrate any selective antitumor activity. In addition, 6-methyl-9-(β-d-arabinofuranosyl)purine (18) was prepared and evaluated.
Topics: Animals; Antineoplastic Agents; Catalysis; Cell Line; Cell Line, Tumor; Escherichia coli; Halogenation; Humans; Mice; Palladium; Purine Nucleosides; Purine-Nucleoside Phosphorylase; Ribonucleosides; Xenograft Model Antitumor Assays; Zinc
PubMed: 22112758
DOI: 10.1016/j.ejmech.2011.10.039 -
The Journal of Clinical Investigation Aug 2022Purine nucleoside phosphorylase (PNP) enables the breakdown and recycling of guanine nucleosides. PNP insufficiency in humans is paradoxically associated with both...
Purine nucleoside phosphorylase (PNP) enables the breakdown and recycling of guanine nucleosides. PNP insufficiency in humans is paradoxically associated with both immunodeficiency and autoimmunity, but the mechanistic basis for these outcomes is incompletely understood. Here, we identify two immune lineage-dependent consequences of PNP inactivation dictated by distinct gene interactions. During T cell development, PNP inactivation is synthetically lethal with downregulation of the dNTP triphosphohydrolase SAMHD1. This interaction requires deoxycytidine kinase activity and is antagonized by microenvironmental deoxycytidine. In B lymphocytes and macrophages, PNP regulates Toll-like receptor 7 signaling by controlling the levels of its (deoxy)guanosine nucleoside ligands. Overriding this regulatory mechanism promotes germinal center formation in the absence of exogenous antigen and accelerates disease in a mouse model of autoimmunity. This work reveals that one purine metabolism gene protects against immunodeficiency and autoimmunity via independent mechanisms operating in distinct immune lineages and identifies PNP as a potentially novel metabolic immune checkpoint.
Topics: Animals; Autoimmunity; Humans; Immunologic Deficiency Syndromes; Mice; Purine Nucleosides; Purine-Nucleoside Phosphorylase; T-Lymphocytes; Toll-Like Receptor 7
PubMed: 35653193
DOI: 10.1172/JCI160852 -
PloS One 2023Malaria remains a major public health threat for billions of people worldwide. Infection with obligate intracellular, unicellular parasites from the genus Plasmodium...
Malaria remains a major public health threat for billions of people worldwide. Infection with obligate intracellular, unicellular parasites from the genus Plasmodium causes malaria. Plasmodium falciparum causes the deadliest form of human malaria. Plasmodium parasites are purine auxotrophic. They rely on purine import from the host red blood cell cytoplasm via equilibrative nucleoside transporters to supply substrates to the purine salvage pathway. We previously developed a high throughput screening assay to identify inhibitors of the P. falciparum Equilibrative Nucleoside Transporter Type 1 (PfENT1). Screening a small molecule library identified PfENT1 inhibitors that blocked proliferation of P. falciparum parasites in in vitro culture. The goal of the current work was to validate a high-resolution model of PfENT1 predicted by the AlphaFold protein structure prediction program. We superimposed the predicted PfENT1 structure on the human homologue structure, hENT1, and developed a structure-based sequence alignment. We mutated the residues in PfENT1 aligned with and flanking the residues in hENT1 that interact with the purine analog, nitrobenzylthioinosine (NBMPR). Mutation of the PfENT1 residues Q135, D287, and R291 that are predicted to form hydrogen bonds to purine nucleosides eliminated purine and pyrimidine transport function in various yeast-based growth and radiolabeled substrate uptake assays. Mutation of two flanking residues, W53 and S290, also resulted in inactive protein. Mutation of L50 that forms hydrophobic interactions with the purine nucleobase reduced transport function. Based on our results the AlphaFold predicted structure for PfENT1 may be useful in guiding medicinal chemistry efforts to improve the potency of our PfENT1 inhibitors.
Topics: Animals; Humans; Purine Nucleosides; Parasites; Nucleobase, Nucleoside, Nucleotide, and Nucleic Acid Transport Proteins; Malaria, Falciparum; Membrane Transport Proteins; Malaria; Saccharomyces cerevisiae; Equilibrative Nucleoside Transporter 1
PubMed: 38113238
DOI: 10.1371/journal.pone.0293923 -
Cellular and Molecular Life Sciences :... Apr 2003The purine nucleoside cycle is a cyclic pathway composed of three cytosolic enzymes, hypoxanthine-guanine phosphoribosyltransferase, IMP-GMP specific 5'-nucleotidase,...
The purine nucleoside cycle is a cyclic pathway composed of three cytosolic enzymes, hypoxanthine-guanine phosphoribosyltransferase, IMP-GMP specific 5'-nucleotidase, and purine-nucleoside phosphorylase. It may be considered a 'futile cycle', whose net reaction is the hydrolysis of 5-phosphoribosyl-1-pyrophosphate to inorganic pyrophosphate and ribose 1-phosphate. The availability of a highly purified preparation of cytosolic 5'-nucleotidase prompted us to reconstitute the purine nucleoside cycle. Its kinetics were strikingly similar to those observed when dialyzed extracts of rat brain were used. Thus, when the cycle is started by addition of inorganic phospate (Pi) and hypoxanthine or inosine (the 'inosine cycle'), steady-state levels of the intermediates are observed and the cycle 'turns over' as far as 5-phosphoribosyl-1-pyrophosphate is being consumed. In the presence of ATP, which acts both as an activator of IMP-GMP-specific 5'-nucleotidase and as substrate of nucleoside mono- and di-phosphokinases, no IDP and ITP are formed. The inosine cycle is further favored by the extremely low xanthine oxidase activity. Evidence is presented that ribose 1-phosphate needed to salvage pyrimidine bases in rat brain may arise, at least in part, from the 5-phosphoribosyl-1-pyrophosphate hydrolysis as catalyzed by the inosine cycle, showing that it may function as a link between purine and pyrimidine salvage. When the cycle is started by addition of Pi and guanine (the 'guanosine cycle'), xanthine and xanthosine are formed, in addition to GMP and guanosine, showing that the guanosine cycle 'turns over' in conjunction with the recycling of ribose 1-phosphate for nucleoside interconversion. In the presence of ATP, GDP and GTP are also formed, and the velocity of the cycle is drastically reduced, suggesting that it might metabolically modulate the salvage synthesis of guanyl nucleotides.
Topics: Animals; Brain; Fluorouracil; Guanosine; Inosine; Male; Phosphoribosyl Pyrophosphate; Purine Nucleosides; Pyrimidines; Rats; Rats, Sprague-Dawley; Ribosemonophosphates
PubMed: 12785725
DOI: 10.1007/s00018-003-2371-x