Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Deoxyadenosine and deoxyguanosine are toxic to human lymphoid cells in culture and have been implicated in the pathogenesis of the immunodeficiency states associated with adenosine deaminase and purine nucleoside phosphorylase deficiency, respectively. We have studied the relative incorporation of several labeled nucleosides into DNA and into nucleotide pools to further elucidate the mechanism of deoxyribonucleoside toxicity. In the presence of an inhibitor of adenosine deaminase [erythro-9-(2-hydroxy-3-nonyl)adenine [EHNA], 5 muM], deoxyadenosine (1-50 muM) progressively decreased the incorporation of thymidine, uridine, and deoxyuridine into DNA, but did not affect uridine incorporation into RNA. This decrease in DNA synthesis was associated with increasing dATP and decreasing dCTP pools. Likewise, incubation of cells with deoxyguanosine caused an elevation of dGTP, depletion of dCTP, and inhibition of DNA synthesis. To test the hypothesis that dATP and dGTP accumulation inhibit DNA synthesis by inhibiting the enzyme ribonucleotide reductase, simultaneous rates of incorporation of [(3)H]uridine and [(14)C]thymidine into DNA were measured in the presence of deoxyadenosine plus EHNA or deoxyguanosine, and in the presence of hydroxyurea, a known inhibitor of ribonucleotide reductase. Hydroxyurea (100 muM) and deoxyguanosine (10 muM) decreased the incorporation of [(3)H]uridine but not of [(14)C]thymidine into DNA; both compounds also substantially increased [(3)H]cytidine incorporation into the ribonucleotide pool while reducing incorporation into the deoxyribonucleotide pool. In contrast, deoxyadenosine plus EHNA did not show this differential inhibition of [(3)H]uridine incorporation into DNA, and the alteration in [(3)H]cytidine incorporation into nucleotide pools was less impressive. These data show an association between accumulation of dATP or dGTP and a primary inhibition of DNA synthesis, and they provide support for ribonucleotide reductase inhibition as the mechanism responsible for deoxyguanosine toxicity. Deoxyadenosine toxicity, however, appears to result from another, or perhaps a combination of, molecular event(s).
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PMID:Purinogenic immunodeficiency diseases. Differential effects of deoxyadenosine and deoxyguanosine on DNA synthesis in human T lymphoblasts. 11 1

Deoxyadenosine at low concentrations and in the presence of an inhibitor of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) is markedly toxic to lymphoblast cell lines of T cell origin but does not impair growth of B cell lines. Deoxyguanosine is also more toxic for T lymphoblasts. In the presence of deoxyadenosine or deoxyguanosine, elevation of the corresponding deoxyribonucleoside triphosphate (dATP or dGTP) occurs in T cell, but not in B cell, lines. The addition of deoxycytidine or dipyridamole results in lower dATP and dGTP levels and prevents deoxyribonucleoside toxicity. These findings provide a molecular basis for the immunodeficiency observed in individuals with several inborn errors of purine metabolism.
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PMID:Purinogenic immunodeficiency diseases: selective toxicity of deoxyribonucleosides for T cells. 31 Oct 4

Two enzymes participating in 2'-deoxyadenosine (dAdo) metabolism: dAdo kinase (dAdoK EC 2.7.1.76) and adenosine deaminase (ADA, EC 3.5.4.4) were partially purified from rat liver mitochondria and cytosol and influence of nucleosides and nucleotides on the activity of these enzymes were investigated. Mitochondrial and cytosol dAdoK are separate proteins, while ADA from both subcellular fractions possesses similar physical properties. dGTP, a competitive inhibitor of mitochondrial dAdoK, inhibits cytosol ADA in a mixed way but activates mitochondrial ADA and cytosol dAdoK. A possible effect of dGTP on dAdo metabolism in mitochondria and cytosol is discussed.
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PMID:Different effect of dGTP on 2'-deoxyadenosine metabolism in mitochondria and cytosol. 133 28

Hydroxyurea, an inhibitor of ribonucleotide reductase, blocks replication of vaccinia virus. However, when medium containing hydroxyurea and dialyzed serum was supplemented with deoxyadenosine, the block to viral reproduction was circumvented, provided that an inhibitor of adenosine deaminase was also present. Deoxyguanosine, deoxycytidine, and deoxythymidine were ineffective alone and did not augment the deoxyadenosine effect. In fact, increasing concentrations of deoxyguanosine and deoxythymidine, but not deoxycytidine, eliminated the deoxyadenosine rescue, an effect that was reversed by the addition of low concentrations of deoxycytidine. These results suggested that the inhibition of viral replication by hydroxyurea was primarily due to a deficiency of dATP. Deoxyribonucleoside triphosphate pools in vaccinia virus-infected cells were measured at the height of viral DNA synthesis after a synchronous infection. With 0.5 mM hydroxyurea, the dATP pool was greater than 90% depleted, the dCTP and dGTP pools were 40 to 50% reduced, and the dTTP pool was increased. Assay of ribonucleotide reductase activity in intact virus-infected cells suggested that hydroxyurea may differentially affect reduction of the various substrates of the enzyme.
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PMID:Deoxyadenosine reverses hydroxyurea inhibition of vaccinia virus growth. 201 60

2,6-Diaminopurine (DAP) and 2,6-diaminopurine 2'-deoxyriboside (DAPdR) are analogs of adenine and deoxyadenosine, respectively. It was the purpose of this study to compare these analogs under identical conditions in order to define their inhibitory properties and the underlying mechanism in L1210 mouse leukemia cells. In a 5-day cell growth experiment, DAP exerted a significantly stronger antiproliferative effect than DAPdR. Correspondingly, colony formation of L1210 cells in soft agarose was inhibited by DAP to a greater extent than by DAPdR. A differential distribution of L1210 cells in the cell cycle resulted from an exposure to DAP and DAPdR. While DAPdR arrested cells in the G1/G0 phase of the cell cycle, DAP appeared to lead to an accumulation of G2/M cells. The diaminopurines were combined with modulatory agents to test the antiproliferative action of the combinations. Deoxycytidine partially rescued the cells from the growth inhibitory action of DAPdR without affecting the growth of DAP-treated cells. When adenine was used, the antiproliferative effect of DAPdR was slightly enhanced while the effect of DAP was completely abolished. 8-Aminoguanosine, a specific inhibitor of purine nucleoside phosphorylase, synergistically potentiated the cytostatic effect of DAPdR. However, this inhibitor did not alter DAP effects. At the biochemical level, the target of DAPdR was ribonucleotide reductase which was in line with a drastic expansion of the dGTP pool in DAPdR-treated cells. In cells exposed to DAP, high levels of DAP riboside triphosphate were measured; concomitantly, the ATP level dropped markedly. Enzymological studies revealed that DAPdR is an excellent substrate of adenosine deaminase giving rise to the formation of deoxyguanosine. DAP was found to be activated in the purine nucleoside phosphorylase reaction and in a phosphoribosyl-pyrophosphate-dependent reaction. The data from this comparative study suggest that DAPdR and DAP possess different toxicity mechanisms. DAPdR and DAP possess different toxicity mechanisms. DAPdR acts as a precursor of deoxyguanosine, and DAP is metabolically activated to DAP-containing ribonucleotide analogs. These different metabolic routes seem to account for the different effects of DAP and DAPdR at the cellular level.
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PMID:Metabolic activation of 2,6-diaminopurine and 2,6-diaminopurine-2'-deoxyriboside to antitumor agents. 262 71

Hydroxyurea-resistant S49 T-lymphoma cells have increased ribonucleotide reductase activity and deoxyribonucleoside triphosphate pools when compared with wild-type cultures. If ribonucleotide reductase inhibition is the mechanism by which deoxyadenosine is cytotoxic, then hydroxyurea (HU)-resistant S49 cells might be more resistant to deoxyadenosine toxicity when adenosine deaminase is inhibited than wild-type cells. Five S49 cell lines resistant to varying concentrations of HU were compared with wild-type cells by measuring CDP reductase activity, deoxyribonucleoside triphosphate pools, and deoxyadenosine toxicity. All five cell lines resistant to increasing concentrations of HU exhibited a twofold increase in resistance to deoxyadenosine toxicity when compared to wild type, and the resistance was proportional to the twofold increased pools of dNTPs in these cell lines but was less than the six- to eight fold increase in ribonucleotide reductase activity. In both wild-type and mutant cell lines, deoxyadenosine toxicity was accompanied by the accumulation of deoxyadenosine triphosphate and reduction of the other dNTPs; however, only dGTP greatly diminished. Exogenous addition of deoxycytidine decreased the dATP accumulation by about 20%, but also resulted in increases in the dCTP, dTTP, and dGTP pools. The S49 cells arrested in G1 phase when exposed to dAdo, although hydroxyurea-resistant cells required higher dAdo concentrations to elicit G1-phase arrest than wild-type cells. Deoxycytidine prevented dAdo-induced G1 arrest in all cell types. In summary, these data support the hypothesis that deoxyadenosine-induced dATP accumulation results in inhibition of ribonucleotide reductase and that this may be the mechanism for both cell cycle arrest and cytotoxicity in S49 T-lymphoma cells.
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PMID:Deoxyadenosine toxicity and cell cycle arrest in hydroxyurea-resistant S49 T-lymphoma cells. 305 32

Some biochemical mechanisms underlying the impairments of cellular immunity were studied in C3Ha mice in the course of growth of transplantable and induced (ortoaminoazotoluol) solid hepatomas. During intensive hepatoma growth, the adenosine deaminase activity in host thymocytes was shown to be drastically (6 times) reduced, resulting in the elevation of dATP and dGTP concentrations (6- and 7-fold, respectively), the potential inhibitors of ribonucleoside diphosphate reductase. Consequently, the rate of DNA synthesis was reduced as can be evidenced by the decrease of (a) thymidine kinase activity, (b) 14C-thymidine incorporation into DNA, and (c) dTTP and dCTP pools. By the terminal period of hepatoma growth (both transplantable and induced one), the serum corticosterone content increased 3- and 8-fold, respectively. At the same time, specific binding of [3H]triamsinolone acetonide by thymocytes was augmented and the activity of terminal deoxynucleotidyl transferase increased the latter alterations, which can be regarded as a reflection (including other parameters mentioned) of the arrest of T-lymphocyte differentiation at the level of immature cortex thymocytes.
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PMID:[Changes in the lymphoid cells of DNA and purine nucleotide synthesis and sensitivity to glucocorticoids associated with impairment of differentiation and immune function during tumor growth in mice. Thymocytes]. 308 74

Biochemical impairments in spleen immunocompetent cells (T- and B-lymphocytes) were revealed in host (C3HA mice) of transplantable and ortoaminoazotoluol-induced hepatomas in the course of their growth. As soon as hepatoma emerged (chemical carcinogenesis), the activity of adenosine deaminase and purine nucleoside phosphorylase in T- and B-lymphocytes were found to be reduced 2-6 and 7-10-fold, respectively in parallel with the impairment of their immune system. These alterations were accompanied by the increase in concentrations of dGTP in T-lymphocytes (5.4-fold) and of dATP in B-lymphocytes (4-fold) as well as with the inhibition of DNA synthesis, predominantly in T-lymphocytes. In both T- and B-lymphocytes, the dCTP pool was decreased. In the spleen, T- and B-lymphocytes of mice carrying transplantable 22 hepatoma 22 by the moment of its maximal growth (5th day), the DNA synthesis was inhibited as revealed by the reduction of (a) thymidine kinase activity, (b) rate of the labeled thymidine incorporation into DNA, and (c) intracellular dTTP and dCTP concentrations. In latter periods (from 8th day up to the moment of death), drastic stimulation of DNA synthesis in spleen T- and B-lymphocytes was observed irrespective of the impairments in the immune function and the decrease of the adenosine deaminase activity. In the course of growth of both transplantable and induced solid hepatomas in host spleen T- lymphocytes, the activity of the CTP-dependent thymidine kinase isoenzyme increased, coinciding in time with the activation of antigen-specific T-suppressors in the same organ.
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PMID:[Changes in DNA and purine nucleotide synthesis in lymphoid cells and sensitivity to glucocorticoids associated with the impairment of differentiation and immune function in mice during tumor growth. Spleen T- and B-lymphocytes]. 308 34

This paper compares erythrocyte nucleotide levels in patients with eight different inherited purine or pyrimidine enzyme defects identified amongst a variety of patients referred predominantly for investigation of severe neurological abnormalities, or immunodeficiency syndromes. Characteristic nucleotide patterns were identified only in the six disorders (four involving purine and two pyrimidine metabolism) where there was clinical evidence of cellular toxicity. They were frequently related to the accumulation of abnormal metabolites in body fluids. These erythrocyte studies have demonstrated the following. 1. ATP depletion is not an invariable feature of adenosine deaminase (ADA) deficiency, but the accumulation of the deoxyribonucleotides dATP, or dGTP, is diagnostic of ADA, or purine nucleoside phosphorylase (PNP) deficiency, respectively. The early accumulation of dATP in foetal blood is a valuable aid to prenatal diagnosis of ADA deficiency. 2. GTP depletion appears to reflect the degree of CNS involvement in hypoxanthine-guanine phosphoribosyltransferase and PNP deficiency, as well as PP-ribose-P synthetase superactivity. Other diagnostic changes involving increased pyrimidine sugars and increased or decreased NAD levels, or ZTP in Lesch Nyhan erythrocytes, show no consistent correlation with the clinical manifestations. 3. These altered nucleotide levels afford a novel means for carrier detection of the X-linked defect associated with aberrant PP-ribose-P synthetase activity, where no other test is yet available. Measurement of erythrocyte nucleotide levels thus provides a simple and rapid aid to diagnosis and may sometimes be essential for determining prognosis, carrier detection, or monitoring therapy. These characteristic 'fingerprints' may give some insight into the mechanism by which the abnormal gene product produces disease. Such grossly altered nucleotide levels could also result in loss of erythrocyte flexibility, increased destruction and hence the anaemia, or other clinical manifestations, observed in some disorders.
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PMID:Altered erythrocyte nucleotide patterns are characteristic of inherited disorders of purine or pyrimidine metabolism. 337 Aug 20

In thymocytes of C3HA mice carrying the transplantable and ortoaminoazotoluene induced hepatomas at the time of their intense growth a drastic decrease in adenosine deaminase activity set in and 3-4-fold augmentation of intracellular concentration of dATP and dGTP, potential inhibitors of ribonucleoside diphosphate reductase was observed, leading to the reduction of the DNA synthesis. The latter event was evidenced by a suppressed 14C-thymidine incorporation into thymocytes DNA in vitro, decreased thymidine kinase activity, intracellular dTTP and depletion of dCTP pools. Only in the terminal period of hepatocarcinogenesis (12 months) a 4-fold increase in the corticosterone serum concentration was observed. As for the mice carrying transplantable 22a hepatoma, serum hormone levels augmented 4-fold as early as 24 h after tumor implantation and thereafter kept increased two fold. An elevated activity of terminal deoxynucleotidyl transferase in mouse thymocytes has been shown to be characteristic of the late periods of tumor growth reflecting the arrest of the immature cortical thymocyte differentiation. By the time hepatomas emerged in the course of hepatocarcinogenesis in spleen T and B lymphocytes a significant drop in the activity of adenosine deaminase (3-4-fold) and purine nucleoside phosphorylase (2-8-fold) was noted--the events directly correlated with the weakening of cell immune functions. The disorders described were accompanied by the accumulation of dGTP in spleen T lymphocytes, dATP in B lymphocytes and inhibition of DNA synthesis, predominantly in T lymphocytes. In the latter instance the pool of dCTP was found to be depleted. In spleen T and B lymphocytes of mice carrying solid 22a hepatoma when the peak of its growth was reached (day 5) the rate of DNA synthesis dropped. Later on (from day 8 to the animal death), however, in spite of the suppression of immune function and the decrease in adenosine deaminase activity a drastic stimulation of DNA synthesis in spleen T and B lymphocytes was observed. The increase in spleen T suppressor activity in the course of intense growth of the both types of hepatomas coincided in the time with the stimulation of the CTP-dependent thymidine kinase isoenzyme activity in total T lymphocyte population of the same organ.
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PMID:Some biochemical mechanisms underlying the impairment of T and B cell immunity in C3HA mice during hepatoma growth. 349 9


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