Nucleotide and Nucleoside Analogues as Inhibitors of Cytosolic 5‘-Nucleotidase I from Heart

Garvey, Edward P.; Lowen, Gregory T.; Almond, Merrick R.

doi:10.1021/bi980209d

Cited by 34 publications

(36 citation statements)

References 33 publications

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“…Although the enzyme had a lower specific activity with pyrimidine deoxyribonucleoside monophosphates, when catalytic efficiency was assessed by the V max /K m ratio, dCMP was 21 times more efficient as a substrate than AMP. Similar results were reported for the rabbit cN-I enzyme (17). Although the K m values for TMP and dUMP were not determined, based on the rabbit enzyme data they are also likely to be efficient substrates of cN-I.…”

Section: Discussionsupporting

confidence: 75%

“…In rat heart, control ADP concentrations of 64 M increase to 106 M under hypoxic conditions (32). These fluctuations in ADP levels are precisely within the range of A 0.5 value for this activator and further signify the important role of this enzyme in adenosine generation in the heart during ischemia (15,17,24) and potentially also in working skeletal muscle. Interestingly, recombinant human cN-I is also significantly activated by GTP, and an increase in GTP levels, for example during cellular proliferation, may also play a role in activation of the enzyme.…”

Section: Discussionsupporting

confidence: 54%

“…From the characteristics of the purified cN-I enzyme and the cloned pigeon cN-I enzyme, cN-I has been identified as the enzyme responsible for most of the adenosine production in hypoxic and ischemic heart tissue (15,19,24,30). Although cN-I has been purified and characterized from rabbit, rat, pigeon, dog, and human hearts, there is only limited information on its role in pyrimidine metabolism (17,20). As has been shown for the purified cN-I enzymes, recombinant human cN-I showed the highest specific activity with AMP as a substrate.…”

Section: Discussionmentioning

confidence: 99%

“…Recombinant human cN-I was purified using a modification of previously published protocols for purification of the rabbit enzyme (16,17). Sf9 cells (7.7 g) were resuspended in 40 ml of extraction buffer containing 40 mM NaHEPES, pH 7.0, 15% glycerol, 1 mM EDTA, 1 mM dithiothreitol, 0.2 mM phenylmethylsulfonyl fluoride, 5 mM benzamidine, and 1ϫ complete protease inhibitor mixture (Roche Molecular Biochemicals).…”

Section: Purification Of Cn-imentioning

confidence: 99%

“…This 5Ј-nucleotidase is activated by ADP and prefers AMP to IMP as a substrate (20). Although recent kinetic data suggest that cN-I may participate in deoxyribonucleoside monophosphate catabolism (17), the role of this enzyme in nucleoside analog resistance has never been examined. Thus we hypothesize that cN-I might play a role in dephosphorylation of deoxyribonucleoside monophosphates and in inactivation of nucleoside analogs.…”

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confidence: 99%

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Human Cytosolic 5′-Nucleotidase I

Hunsucker

Spychała

Mitchell

2001

Journal of Biological Chemistry

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Nucleoside analogs are important in the treatment of hematologic malignancies, solid tumors, and viral infections. Their metabolism to the triphosphate form is central to their chemotherapeutic efficacy. Although the nucleoside kinases responsible for the phosphorylation of these compounds have been well described, the nucleotidases that may mediate drug resistance through dephosphorylation remain obscure. We have cloned and characterized a novel human cytosolic 5-nucleotidase ( Nucleoside analogs are used as chemotherapeutic agents in the treatment of hematologic malignancies and as anti-viral drugs. These compounds are taken up by cells through nucleoside transporters in the cell membrane or, in the case of more lipophilic drugs, through diffusion (1-3). Once in the cytoplasm, the nucleoside analogs are substrates for phosphorylation by the nucleoside kinases of the deoxyribonucleoside salvage pathway (reviewed in Ref. 4). The enzyme 2Ј-deoxycytidine kinase phosphorylates dAdo, dCyd, and dGuo as well as the analogs AraC, 1 dFdC, and CdA, whereas thymidine kinase 1 phosphorylates dThd and dUrd as well as the analogs d4T and 5-FU. Phosphorylation to the monophosphate form is considered the rate-limiting step of activation of nucleoside analogs (4). Nucleoside analog monophosphates are rapidly phosphorylated to their triphosphate forms, which are believed to mediate their cytotoxic activities by several different mechanisms (reviewed in Ref. 5). For example, they can be directly incorporated into DNA, leading to chain termination, or they can inhibit DNA synthesis by direct inhibition of DNA polymerase. It has recently been demonstrated that certain of these metabolites, including CdATP, AraATP, and F-AraATP, can induce apoptosis in nonproliferating cells by interacting with cytochrome c and apoptosis protein-activating factor-1 (APAF-1) to cleave and activate the caspases responsible for the induction of apoptosis (6, 7). In contrast, the triphosphates of antiretroviral compounds, such as 2Ј,3Ј-dideoxycytidine (ddC) and d4T, inhibit the reverse transcriptase of the human immunodeficiency virus through chain termination. Cytotoxicity can occur when these compounds are incorporated into nuclear or mitochondrial DNA (reviewed in Ref. 8).Resistance to nucleoside analogs is a significant clinical problem and can be caused by a number of factors affecting the metabolism of the drugs, including decreased numbers of nucleoside transporters, increased deamination of cytidine and adenosine analogs, loss of expression of activating kinases, modulation of the downstream apoptotic machinery, and increased activity of nucleotidases that catalyze the conversion of nucleotides back to nucleosides (reviewed in Ref. 5). The 5Ј-nucleotidases oppose the action of nucleoside kinases by dephosphorylating the monophosphate form of nucleosides and nucleoside analogs and, therefore, are likely to be important in determining the sizes and turnover rates of the deoxyribonucleotide pools. Thus, 5Ј-nucleotidases that catabolize the monophos...

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Section: Discussionsupporting

confidence: 75%

Section: Discussionsupporting

confidence: 54%

Section: Discussionmentioning

confidence: 99%

Section: Purification Of Cn-imentioning

confidence: 99%

mentioning

confidence: 99%

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Human Cytosolic 5′-Nucleotidase I

Hunsucker

Spychała

Mitchell

2001

Journal of Biological Chemistry

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Electrophilic Fluorination withN–FReagents

Baudoux

Cahard

2008

Organic Reactions

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The synthesis of selectively fluorinated molecules is an important challenge in organic chemistry. This topic has received considerable attention because of the utility of fluorinated compounds in a wide variety of disciplines. There are three types of fluorination depending on whether the fluorine atom is radical, anionic, or cationic. Fluorine radicals are of little synthetic use because of the difficulties in controlling their reactivity. Fluorine is utilized in nucleophilic as well as electrophilic fluorinations Molecular fluorine is the simplest reagent of this type, however, its safe handling is difficult. Stable, selective reagents are crucial to the development of electrophilic fluorination. N‐F reagents have emerged as generally safer and easier to handle selective sources of electrophilic fluorine. N‐F reagents offer a range of fluorinating powers and some are available commercially. Two classes are known: neutral N‐F reagents and quaternary ammonium N‐F reagents (quaternary salts are usually the more powerful). N‐F reagents popularity arises because they posses a long shelf life, several are commercially available, and they can be handled safely in glassware. The drawback is the preferential use of molecular fluorine for their preparation. This article deals with the preparation and the use of all types of electrophilic fluorinating agents possessing the N‐F moiety.

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Proton affinity ladder for uridine and analogs: influence of the hydroxyl group on the sugar ring conformation

Mezzache¹,

Alvès²,

Pèpe³

et al. 2005

J. Mass Spectrom.

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A ladder of relative proton affinities (PA) for a series of modified uridines (e.g. araU, ddU, 5BrU, 5BrdU and 5IU) was established from competitive dissociations of proton-bound heterodimers using Cooks and co-workers' kinetic method. The studied heterodimers are constituted of a modified nucleoside and either an amino acid or a nucleoside with known PA value. These non-covalent heterodimers were prepared under electrospray conditions to be selected and dissociated into the ion-trap analyzer. These results allowed our PA ladder of uridine and deoxyuridine analogs substituted at the C-5 position in the uracil ring to be extended. From this scale, it was showed that the substitution of hydrogen atom at the C-2' position in the sugar ring by a hydroxyl group involves a decrease of about 7 kJ mol(-1). The experimental values for U, 5MeU, dU, 5MedU, ddU and araU are consistent with those obtained by DFT calculations (B3P86/6-31+G//B3LYP/6-31G(.)). Several neutral and protonated conformations of these compounds were considered, in particular the ring conformation of furanose and the orientation of the base with respect to the sugar ring. These calculated results showed the influence of sugar substituent on the conformation of the neutral form of theses nucleosides. However, the most stable protonated structure is the same for all the studied nucleosides except for araU, where the position of the anti 2'-OH group imposes a specific conformation.

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Nucleotide and Nucleoside Analogues as Inhibitors of Cytosolic 5‘-Nucleotidase I from Heart

Cited by 34 publications

References 33 publications

Human Cytosolic 5′-Nucleotidase I

Human Cytosolic 5′-Nucleotidase I

Electrophilic Fluorination withN–FReagents

Proton affinity ladder for uridine and analogs: influence of the hydroxyl group on the sugar ring conformation

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