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Piero Luigi Ipata - One of the best experts on this subject based on the ideXlab platform.
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Pentose Phosphates in nucleoside interconversion and catabolism
FEBS Journal, 2006Co-Authors: Maria Grazia Tozzi, Laura Mascia, Francesco Sgarrella, Marcella Camici, Piero Luigi IpataAbstract:Ribose Phosphates are either synthesized through the oxidative branch of the pentose Phosphate pathway, or are supplied by nucleoside phosphorylases. The two main pentose Phosphates, Ribose-5-Phosphate and Ribose-1-Phosphate, are readily interconverted by the action of phosphopentomutase. Ribose-5-Phosphate is the direct precursor of 5-phosphoribosyl-1-pyroPhosphate, for both de novo and 'salvage' synthesis of nucleotides. Phosphorolysis of deoxyribonucleosides is the main source of deoxyRibose Phosphates, which are interconvertible, through the action of phosphopentomutase. The pentose moiety of all nucleosides can serve as a carbon and energy source. During the past decade, extensive advances have been made in elucidating the pathways by which the pentose Phosphates, arising from nucleoside phosphorolysis, are either recycled, without opening of their furanosidic ring, or catabolized as a carbon and energy source. We review herein the experimental knowledge on the molecular mechanisms by which (a) Ribose-1-Phosphate, produced by purine nucleoside phosphorylase acting catabolically, is either anabolized for pyrimidine salvage and 5-fluorouracil activation, with uridine phosphorylase acting anabolically, or recycled for nucleoside and base interconversion; (b) the nucleosides can be regarded, both in bacteria and in eukaryotic cells, as carriers of sugars, that are made available though the action of nucleoside phosphorylases. In bacteria, catabolism of nucleosides, when suitable carbon and energy sources are not available, is accomplished by a battery of nucleoside transporters and of inducible catabolic enzymes for purine and pyrimidine nucleosides and for pentose Phosphates. In eukaryotic cells, the modulation of pentose Phosphate production by nucleoside catabolism seems to be affected by developmental and physiological factors on enzyme levels.
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The purine nucleoside cycle in cell-free extracts of rat brain: evidence for the occurrence of an inosine and a guanosine cycle with distinct metabolic roles
Cellular and Molecular Life Sciences, 2003Co-Authors: Catia Barsotti, Rossana Pesi, Francesca Felice, Piero Luigi IpataAbstract: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.
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purine and pyrimidine salvage in whole rat brain utilization of atp derived Ribose 1 Phosphate and 5 phosphoribosyl 1 pyroPhosphate generated in experiments with dialyzed cell free extracts
Journal of Biological Chemistry, 2002Co-Authors: Catia Barsotti, Maria Grazia Tozzi, Piero Luigi IpataAbstract:Abstract The object of this work stems from our previous studies on the mechanisms responsible of Ribose-1-Phosphate- and 5-phosphoribosyl-1-pyroPhosphate-mediated nucleobase salvage and 5-fluorouracil activation in rat brain (Mascia, L., Cappiello M., Cherri, S., and Ipata, P. L. (2000) Biochim. Biophys. Acta 1474, 70–74; Mascia, L., Cotrufo, T., Cappiello, M., and Ipata, P. L. (1999) Biochim. Biophys. Acta 1472, 93–98). Here we show that when ATP at “physiological concentration” is added to dialyzed extracts of rat brain in the presence of natural nucleobases or 5-fluorouracil, adenine-, hypoxanthine-, guanine-, uracil-, and 5-fluorouracil-ribonucleotides are synthesized. The molecular mechanism of this peculiar nucleotide synthesis relies on the capacity of rat brain to salvage purine and pyrimidine bases by deriving Ribose-1-Phosphate and 5-phosphoribosyl-1-pyroPhosphate from ATP even in the absence of added pentose or pentose Phosphates. The levels of the two sugar Phosphates formed are compatible with those of synthesized nucleotides. We propose that the ATP-mediated 5-phosphoribosyl-1-pyroPhosphate synthesis occurs through the action of purine nucleoside phosphorylase, phosphopentomutase, and 5-phosphoribosyl-1-pyroPhosphate synthetase. Furthering our previous observations on the effect of ATP in the 5-phosphoribosyl-1-pyroPhosphate-mediated 5-fluorouracil activation in rat liver (Mascia, L., and Ipata, P. L. (2001)Biochem. Pharmacol. 62, 213–218), we now show that the ratio [5-phosphoribosyl-1-pyroPhosphate]/[ATP] plays a major role in modulating adenine salvage in rat brain. On the basis of ourin vitro results, we suggest that massive ATP degradation, as it occurs in brain during ischemia, might lead to an increase of the intracellular 5-phosphoribosyl-1-pyroPhosphate and Ribose-1-Phosphate pools, to be utilized for nucleotide resynthesis during reperfusion.
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Uracil salvage pathway in PC12 cells
Biochimica et Biophysica Acta, 2001Co-Authors: Laura Mascia, Gino Turchi, Valentina Bemi, Piero Luigi IpataAbstract:Abstract The salvage anabolism of uracil to pyrimidine ribonucleosides and ribonucleotides was investigated in PC12 cells. Pyrimidine base phosphoribosyl transferase is absent in PC12 cells. As a consequence any uracil or cytosine salvage must be a 5-phosphoribosyl 1-pyroPhosphate-independent process. When PC12 cell extracts were incubated with Ribose 1-Phosphate, ATP and uracil they can readily catalyze the synthesis of uracil nucleotides, through a salvage pathway in which the Ribose moiety of Ribose 1-Phosphate is transferred to uracil via uridine phosphorylase (acting anabolically), with subsequent uridine phosphorylation. This pathway is similar to that previously described by us in rat liver and brain extracts (Cappiello et al., Biochim. Biophys. Acta 1425 (1998) 273; Mascia et al., Biochim. Biophys. Acta 1472 (1999) 93). We show using intact PC12 cells that they can readily take up uracil from the external medium. The analysis of intracellular metabolites reveals that uracil taken up is salvaged into uracil nucleotides, with uridine as an intermediate. We propose that the Ribose 1-Phosphate-dependent uracil salvage shown by our in vitro studies, using tissues or cellular extracts, might also be operative in intact cells. Our results must be taken into consideration for the comprehension of novel chemotherapeutics’ influence on pyrimidine neuronal metabolism.
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in vitro recycling of α Ribose 1 Phosphate for the salvage of purine bases
Biochimica et Biophysica Acta, 2000Co-Authors: Laura Mascia, Mario Cappiello, Silvia Cherri, Piero Luigi IpataAbstract:Abstract In this paper, we extend our previous observation on the mobilization of the Ribose moiety from a purine nucleoside to a pyrimidine base, with subsequent pyrimidine nucleotides formation (Cappiello et al., Biochim. Biophys. Acta 1425 (1998) 273–281). The data show that, at least in vitro, also the reverse process is possible. In rat brain extracts, the activated Ribose, stemming from uridine as Ribose 1-Phosphate, can be used to salvage adenine and hypoxanthine to their respective nucleotides. Since the salvage of purine bases is a 5-phosphoribosyl 1-pyroPhosphate-dependent process, catalyzed by adenine phosphoribosyltransferase and hypoxanthine guanine phosphoribosyltransferase, our results imply that Rib-1P must be transformed into 5-phosphoribosyl 1-pyroPhosphate, via the successive action of phosphopentomutase and 5-phosphoribosyl 1-pyroPhosphate synthetase; and ,in fact, no adenosine could be found as an intermediate when rat brain extracts were incubated with adenine, Rib-1P and ATP, showing that adenine salvage does not imply adenine ribosylation, followed by adenosine phosphorylation. Taken together with our previous results on the Rib-1P-dependent salvage of pyrimidine nucleotides, our results give a clear picture of the in vitro Rib-1P recycling, for both purine and pyrimidine salvage.
Tadashi Araki - One of the best experts on this subject based on the ideXlab platform.
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Efficient chemo-enzymatic syntheses of pharmaceutically useful unnatural 2'-deoxynucleosides.
Nucleosides Nucleotides & Nucleic Acids, 2005Co-Authors: Hironori Komatsu, Tadashi ArakiAbstract:Our chemo-enzymatic method was successfully applied to the synthesis of 2-chloro-2′-deoxyadenosine (CdA, cladribine) in two ways: 1) direct conversion of chemically synthesized 2-deoxy-α-D-Ribose 1-Phosphate (dRP) to CdA; 2) a two-step route via 9-(2-deoxy-β-D-ribos-1-yl)-2,6-dichloropurine (Cl2Pu-dR, 5).
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Chemo-enzymatic synthesis of 2′,3′-dideoxy-3′-fluoro-β-d-guanosine via 2,3-dideoxy-3-fluoro-α-d-Ribose 1-Phosphate
Tetrahedron Letters, 2003Co-Authors: Hironori Komatsu, Tadashi ArakiAbstract:Abstract 2,3-Dideoxy-3-fluoro-α- d -Ribose 1-Phosphate 2 was stereoselectively synthesized and converted to 2′,3′-dideoxy-3-fluoro-β- d -guanosine 1 by enzymatic reaction using purine nucleoside phosphorylase. This chemo-enzymatic strategy was first applied to the synthesis of 1 .
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chemo enzymatic synthesis of 2 3 dideoxy 3 fluoro β d guanosine via 2 3 dideoxy 3 fluoro α d Ribose 1 Phosphate
Tetrahedron Letters, 2003Co-Authors: Hironori Komatsu, Tadashi ArakiAbstract:Abstract 2,3-Dideoxy-3-fluoro-α- d -Ribose 1-Phosphate 2 was stereoselectively synthesized and converted to 2′,3′-dideoxy-3-fluoro-β- d -guanosine 1 by enzymatic reaction using purine nucleoside phosphorylase. This chemo-enzymatic strategy was first applied to the synthesis of 1 .
Hironori Komatsu - One of the best experts on this subject based on the ideXlab platform.
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Efficient chemo-enzymatic syntheses of pharmaceutically useful unnatural 2'-deoxynucleosides.
Nucleosides Nucleotides & Nucleic Acids, 2005Co-Authors: Hironori Komatsu, Tadashi ArakiAbstract:Our chemo-enzymatic method was successfully applied to the synthesis of 2-chloro-2′-deoxyadenosine (CdA, cladribine) in two ways: 1) direct conversion of chemically synthesized 2-deoxy-α-D-Ribose 1-Phosphate (dRP) to CdA; 2) a two-step route via 9-(2-deoxy-β-D-ribos-1-yl)-2,6-dichloropurine (Cl2Pu-dR, 5).
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synthesis of 2 deoxy β d Ribose 1 Phosphate nmr comparison and its enzymatic activity for structural elucidation of synthetic α isomer
Nucleosides Nucleotides & Nucleic Acids, 2003Co-Authors: Hironori Komatsu, Ichirou IkedaAbstract:Abstract 2-Deoxy-β-D-Ribose 1-Phosphate (1) was synthesized in a stereoselective manner and isolated with no detectable contamination by its α-isomer (4). Explicit configuration of 4 was first determined by NMR comparison with 1 judging from NOE results and their coupling constants. Natural purine nucleoside phosphorylase (PNPase) did not recognize 1 and gave no products such as α- or β-deoxynucleosides.
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Chemo-enzymatic synthesis of 2′,3′-dideoxy-3′-fluoro-β-d-guanosine via 2,3-dideoxy-3-fluoro-α-d-Ribose 1-Phosphate
Tetrahedron Letters, 2003Co-Authors: Hironori Komatsu, Tadashi ArakiAbstract:Abstract 2,3-Dideoxy-3-fluoro-α- d -Ribose 1-Phosphate 2 was stereoselectively synthesized and converted to 2′,3′-dideoxy-3-fluoro-β- d -guanosine 1 by enzymatic reaction using purine nucleoside phosphorylase. This chemo-enzymatic strategy was first applied to the synthesis of 1 .
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chemo enzymatic synthesis of 2 3 dideoxy 3 fluoro β d guanosine via 2 3 dideoxy 3 fluoro α d Ribose 1 Phosphate
Tetrahedron Letters, 2003Co-Authors: Hironori Komatsu, Tadashi ArakiAbstract:Abstract 2,3-Dideoxy-3-fluoro-α- d -Ribose 1-Phosphate 2 was stereoselectively synthesized and converted to 2′,3′-dideoxy-3-fluoro-β- d -guanosine 1 by enzymatic reaction using purine nucleoside phosphorylase. This chemo-enzymatic strategy was first applied to the synthesis of 1 .
Laura Mascia - One of the best experts on this subject based on the ideXlab platform.
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Pentose Phosphates in nucleoside interconversion and catabolism
FEBS Journal, 2006Co-Authors: Maria Grazia Tozzi, Laura Mascia, Francesco Sgarrella, Marcella Camici, Piero Luigi IpataAbstract:Ribose Phosphates are either synthesized through the oxidative branch of the pentose Phosphate pathway, or are supplied by nucleoside phosphorylases. The two main pentose Phosphates, Ribose-5-Phosphate and Ribose-1-Phosphate, are readily interconverted by the action of phosphopentomutase. Ribose-5-Phosphate is the direct precursor of 5-phosphoribosyl-1-pyroPhosphate, for both de novo and 'salvage' synthesis of nucleotides. Phosphorolysis of deoxyribonucleosides is the main source of deoxyRibose Phosphates, which are interconvertible, through the action of phosphopentomutase. The pentose moiety of all nucleosides can serve as a carbon and energy source. During the past decade, extensive advances have been made in elucidating the pathways by which the pentose Phosphates, arising from nucleoside phosphorolysis, are either recycled, without opening of their furanosidic ring, or catabolized as a carbon and energy source. We review herein the experimental knowledge on the molecular mechanisms by which (a) Ribose-1-Phosphate, produced by purine nucleoside phosphorylase acting catabolically, is either anabolized for pyrimidine salvage and 5-fluorouracil activation, with uridine phosphorylase acting anabolically, or recycled for nucleoside and base interconversion; (b) the nucleosides can be regarded, both in bacteria and in eukaryotic cells, as carriers of sugars, that are made available though the action of nucleoside phosphorylases. In bacteria, catabolism of nucleosides, when suitable carbon and energy sources are not available, is accomplished by a battery of nucleoside transporters and of inducible catabolic enzymes for purine and pyrimidine nucleosides and for pentose Phosphates. In eukaryotic cells, the modulation of pentose Phosphate production by nucleoside catabolism seems to be affected by developmental and physiological factors on enzyme levels.
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Uracil salvage pathway in PC12 cells
Biochimica et Biophysica Acta, 2001Co-Authors: Laura Mascia, Gino Turchi, Valentina Bemi, Piero Luigi IpataAbstract:Abstract The salvage anabolism of uracil to pyrimidine ribonucleosides and ribonucleotides was investigated in PC12 cells. Pyrimidine base phosphoribosyl transferase is absent in PC12 cells. As a consequence any uracil or cytosine salvage must be a 5-phosphoribosyl 1-pyroPhosphate-independent process. When PC12 cell extracts were incubated with Ribose 1-Phosphate, ATP and uracil they can readily catalyze the synthesis of uracil nucleotides, through a salvage pathway in which the Ribose moiety of Ribose 1-Phosphate is transferred to uracil via uridine phosphorylase (acting anabolically), with subsequent uridine phosphorylation. This pathway is similar to that previously described by us in rat liver and brain extracts (Cappiello et al., Biochim. Biophys. Acta 1425 (1998) 273; Mascia et al., Biochim. Biophys. Acta 1472 (1999) 93). We show using intact PC12 cells that they can readily take up uracil from the external medium. The analysis of intracellular metabolites reveals that uracil taken up is salvaged into uracil nucleotides, with uridine as an intermediate. We propose that the Ribose 1-Phosphate-dependent uracil salvage shown by our in vitro studies, using tissues or cellular extracts, might also be operative in intact cells. Our results must be taken into consideration for the comprehension of novel chemotherapeutics’ influence on pyrimidine neuronal metabolism.
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in vitro recycling of α Ribose 1 Phosphate for the salvage of purine bases
Biochimica et Biophysica Acta, 2000Co-Authors: Laura Mascia, Mario Cappiello, Silvia Cherri, Piero Luigi IpataAbstract:Abstract In this paper, we extend our previous observation on the mobilization of the Ribose moiety from a purine nucleoside to a pyrimidine base, with subsequent pyrimidine nucleotides formation (Cappiello et al., Biochim. Biophys. Acta 1425 (1998) 273–281). The data show that, at least in vitro, also the reverse process is possible. In rat brain extracts, the activated Ribose, stemming from uridine as Ribose 1-Phosphate, can be used to salvage adenine and hypoxanthine to their respective nucleotides. Since the salvage of purine bases is a 5-phosphoribosyl 1-pyroPhosphate-dependent process, catalyzed by adenine phosphoribosyltransferase and hypoxanthine guanine phosphoribosyltransferase, our results imply that Rib-1P must be transformed into 5-phosphoribosyl 1-pyroPhosphate, via the successive action of phosphopentomutase and 5-phosphoribosyl 1-pyroPhosphate synthetase; and ,in fact, no adenosine could be found as an intermediate when rat brain extracts were incubated with adenine, Rib-1P and ATP, showing that adenine salvage does not imply adenine ribosylation, followed by adenosine phosphorylation. Taken together with our previous results on the Rib-1P-dependent salvage of pyrimidine nucleotides, our results give a clear picture of the in vitro Rib-1P recycling, for both purine and pyrimidine salvage.
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In vitro recycling of α-?-Ribose 1-Phosphate for the salvage of purine bases
Biochimica et Biophysica Acta, 2000Co-Authors: Laura Mascia, Mario Cappiello, Silvia Cherri, Piero Luigi IpataAbstract:Abstract In this paper, we extend our previous observation on the mobilization of the Ribose moiety from a purine nucleoside to a pyrimidine base, with subsequent pyrimidine nucleotides formation (Cappiello et al., Biochim. Biophys. Acta 1425 (1998) 273–281). The data show that, at least in vitro, also the reverse process is possible. In rat brain extracts, the activated Ribose, stemming from uridine as Ribose 1-Phosphate, can be used to salvage adenine and hypoxanthine to their respective nucleotides. Since the salvage of purine bases is a 5-phosphoribosyl 1-pyroPhosphate-dependent process, catalyzed by adenine phosphoribosyltransferase and hypoxanthine guanine phosphoribosyltransferase, our results imply that Rib-1P must be transformed into 5-phosphoribosyl 1-pyroPhosphate, via the successive action of phosphopentomutase and 5-phosphoribosyl 1-pyroPhosphate synthetase; and ,in fact, no adenosine could be found as an intermediate when rat brain extracts were incubated with adenine, Rib-1P and ATP, showing that adenine salvage does not imply adenine ribosylation, followed by adenosine phosphorylation. Taken together with our previous results on the Rib-1P-dependent salvage of pyrimidine nucleotides, our results give a clear picture of the in vitro Rib-1P recycling, for both purine and pyrimidine salvage.
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Ribose 1 Phosphate and inosine activate uracil salvage in rat brain
Biochimica et Biophysica Acta, 1999Co-Authors: Laura Mascia, Tiziana Cotrufo, Mario Cappiello, Piero Luigi IpataAbstract:Abstract The purpose of this study was to determine the mechanism by which inosine activates pyrimidine salvage in CNS. The levels of cerebral inosine, hypoxanthine, uridine, uracil, Ribose 1-Phosphate and inorganic Phosphate were determined, to evaluate the Gibbs free energy changes (Δ G ) of the reactions catalyzed by purine nucleoside phosphorylase and uridine phosphorylase, respectively. A Δ G value of 0.59 kcal/mol for the combined reaction inosine+uracil⇄uridine+hypoxanthine was obtained, suggesting that at least in anoxic brain the system may readily respond to metabolite fluctuations. If purine nucleoside phosphorolysis and uridine phosphorolysis are coupled to uridine phosphorylation, catalyzed by uridine kinase, whose activity is relatively high in brain, the three enzyme activities will constitute a pyrimidine salvage pathway in which Ribose 1-Phosphate plays a pivotal role. CTP, presumably the last product of the pathway, and, to a lesser extent, UTP, exert inhibition on rat brain uridine nucleotides salvage synthesis, most likely at the level of the kinase reaction. On the contrary ATP and GTP are specific Phosphate donors.
Peter Kuhn - One of the best experts on this subject based on the ideXlab platform.
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structural basis of severe acute respiratory syndrome coronavirus adp Ribose 1 Phosphate dephosphorylation by a conserved domain of nsp3
Structure, 2005Co-Authors: K Saikatendu, Jeremiah S Joseph, V Subramanian, Tom Clayton, Mark T Griffith, Jeffrey Velasquez, Benjamin W Neuman, Michael J Buchmeier, Raymond C Stevens, Peter KuhnAbstract:Summary The crystal structure of a conserved domain of nonstructural protein 3 (nsP3) from severe acute respiratory syndrome coronavirus (SARS-CoV) has been solved by single-wavelength anomalous dispersion to 1.4 A resolution. The structure of this "X" domain, seen in many single-stranded RNA viruses, reveals a three-layered α/β/α core with a macro-H2A-like fold. The putative active site is a solvent-exposed cleft that is conserved in its three structural homologs, yeast Ymx7, Archeoglobus fulgidus AF1521, and Er58 from E. coli . Its sequence is similar to yeast YBR022W (also known as Poa1P), a known phosphatase that acts on ADP-Ribose-1″-Phosphate (Appr-1″-p). The SARS nsP3 domain readily removes the 1″ Phosphate group from Appr-1″-p in in vitro assays, confirming its phosphatase activity. Sequence and structure comparison of all known macro-H2A domains combined with available functional data suggests that proteins of this superfamily form an emerging group of nucleotide phosphatases that dephosphorylate Appr-1″-p.
