Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

A number of infants with an autosomal recessive form of combined immunodeficiency disease also lack adenosine deaminase (adenosine aminohydrolase; EC 3.5.4.4) activity in their erythrocytes. Other tissues from these infants contain only a few percent of the adenosine-deaminating activity present in corresponding normal tissue. The residual adenosine-deaminating activity in extracts from the spleen of a combined immunodeficient, adenosine deaminase-deficient patient was compared with adenosine deaminase from normal spleen. Affinity and immunoadsorbant column chromatography revealed distinct differences between the adenosine-deaminating activity in the patient's spleen and adenosine deaminase from normal spleen. The point of maximum activity and general configuration of the pH optimum curves were also different. erythro-9-(2-Hydroxyl-3-nonyl)adenine, a potent inhibitor of adenosine deaminase from normal spleen, had relatively little effect on the activity from the patient's spleen. In contrast, adenine was a better inhibitor of the activity in the patient's spleen than it was of the enzyme from normal tissue. An adenosine-deaminating activity with the same characteristics and specific activity as that in the patient's spleen was also isolated from normal spleen. These results suggest that the adenosine-deaminating activity in the spleen of this patient is not due to a mutant form of adenosine deaminase.
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PMID:Characterization of the residual adenosine deaminating activity in the spleen of a patient with combined immunodeficiency disease and adenosine deaminase deficiency. 2 16

We have investigated a new hypothesis for the association between adenosine deaminase (A.D.A.) deficiency and immunodeficiency--namely, that deoxyadenosine rather than adenosine (an equally effective A.D.A. substrate) is toxic to proliferating cells of lymphoid origin. This possibility was explored in mitogen-stimulated lymphocytes cultured with a potent A.D.A. inhibitor, E.H.N.A. (erythro-9[2-hydroxy-3-nonyl] adenine) to simulate A.D.A. deficiency. In this in-vitro system deoxyadenosine was inhibitory at much lower and more physiological concentrations (1 mumol/1), compared with adenosine (100 mumol/1).
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PMID:A role for purine metabolism in the immune response: Adenosine-deaminase activity and deoxyadenosine catabolism. 7 65

The antiproliferative activity of 9-beta-D-arabinofuranosyladenine 5'-monophosphate against a cultured line of mouse leukemia cells (L1210/C2) was enhanced by addition of either 2'-deoxycoformycin or erythro-9-(2-hydroxy-3-nonyl)adenine. The activity of 9-beta-D-arabinofuranosyladenine 5'-monophosphate, alone or in combination with either of the two inhibitors of adenosine deaminase, was comparable to that of 9-beta-D-arabinofuranosyladenine (ara-A), apparently reflecting the rapid conversion of 9-beta-D-arabinofuranosyladenine 5'-monophosphate to ara-A by L1210/C2 cells. Several ara-A analogs were assayed for antiproliferative activity against L1210/C2 cells; of these, only 9-beta-D-arabinofuranosyladenine 5'-O-methylphosphate and 2'-deoxy-2'-amino-9-beta-D-arabinofuraosyladenine were active. Addition of 2'-deoxycoformycin to cell culture fluids enhanced the activity of 9-beta-D-arabinofuranosyladenine 5'-O-methylphosphate suggesting conversion to an adenosine deaminase-sensitive intermediate, presumably ara-A.
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PMID:Antiproliferative effects of 9-beta-D-arabinofuranosyladenine 5'-monophosphate and related compounds in combination with adenosine deaminase inhibitors against mouse leukemia L1210/C2 cells in culture. 8 84

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

The biochemical mechanisms by which a genetically determined deficiency of adenosine deaminase leads to immunodeficiency are still poorly understood and prompted this study. We have examined the effects of the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride (EHNA) upon the response of human peripheral blood mononuclear cells to the mitogen concanavalin A (Con A). Cells isolated from normal volunteers were incubated in microtiter plates in the presence of various inhibitors, and the incorporation of tritrated thymidine or leucine into macromolecular material was measured after 64 h. EHNA at a concentration of 0.3 muM, which inhibited 90% of the adenosine deaminase (ADA) activity in a mononuclear preparation, impaired the incorporation of tritrated leucine into protein; 100 muM EHNA was the minimal concentration that inhibited thymidine uptake. The addition of 15 muM adenosine or 10 muM cyclic AMP to Con A-stimulated lymphocytes inhibited leucine uptake, while millimolar concentrations were required to inhibit thymidine uptake. Lower doses of adenosine and cyclic AMP stimulated thymidine incorporation. The inhibition of thymidine uptake observed with millimolar concentrations of adenosine was independent of the type of mitogen (pokeweed or Con A), the concentration of mitogen, or the medium used, but could be increased if the cells were cultured in a serum with reduced levels of adenosine deaminase. Washout experiments failed to demonstrate a critical period early in immune induction during which adenosine exerted its inhibitory effects. Noninhibitory doses of EHNA potentiated the effects of adenosine and cyclic AMP on leucine and thymidine uptake. EHNA at a concentration of 50 muM also potentiated the inhibitory effects on thymidine uptake of dibutyryl cyclic AMP, butyric acid, norepinephrine, and isoproterenol, but not theophylline. When mitogenesis was assayed by leucine incorporations, no synergy between EHNA and these compounds was apparent. Uridine relieved to some extent the inhibition of blastogenesis produced by adenosine and cyclic AMP, but not by dibutyryl cyclic AMP, norepinephreine, isoproterenol, or theophylline. Neither uridine alone nor uridine plus adenosine protected lymphocytes from the inhibitory effects of EHNA.
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PMID:Effect of adenosine deaminase inhibition upon human lymphocyte blastogenesis. 17 77

The absence of erythrocytic adenosine deaminase (ADA) or purine nucleoside phosphorylase (PNP) has been associated with severe immunodeficiency disease in children. We have developed a cell culture model to study the possible relationships between purine salvage enzymes and immunologic function using an established T cell lymphosarcoma (S49) and a potent inhibitor of ADA, erythro-9(2-hydroxy-3-nonyl) adenine (EHNA). Wild-type S49 cells are killed by dexamethasone or dbc AMP, and adenosine (5 muM) in the presence of an ADA inhibitor (6 muM EHNA) also prevents the growth of and kills these S49 cells. It has been proposed that adenosine is toxic to lymphoid cells by virtue of its ability to increase the intracellular concentrations of cyclic AMP. We examined the sensitivity of three mutants of S49 cells, with distinctive defects in some component of cyclic AMP metabolism or action, to killing by adenosine and EHNA. All three mutants are resistant to killing by isoproterenol or cholera toxin and two are resistant to dbc AMP itself, but all are sensitive to killing by adenosine and EHNA. Similarly, two dexamethasone-resistant S49 mutants are as sensitive to adenosine and EHNA as are the wildtype cells. We have also simulated the purine nucleoside phosphorylase deficiency in S49 cells by adding inosine and adenosine to the growth medium. In the presence of EHNA or inosine, the toxic effects of adenosine can be partially reversed by addition of (10-20 muM) uridine, an observation suggesting that adenosine is toxic as the result of its inducing pyrimidine starvation.
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PMID:Characterization of a cell culture model for the study of adenosine deaminase- and purine nucleoside phosphorylase-deficient immunologic disease. 18 61

Erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA; erythro-9-[3-(hydroxynonyl)]adenine), a reversible inhibitor of adenosine deaminase, significantly inhibits replication of herpes simplex virus (HSV), whereas the more active inhibitor of the deaminase, 2'-deoxycoformycin, does not. At 10 micron EHNA, which does not affect viability, growth, or DNA synthesis of uninfected HeLa cells, production of HSV and HSV-specific DNA is inhibited 75-90% and 60%, respectively. HSV multiplies normally in cells pretreated with EHNA and washed to remove this inhibitor. EHNA (10 micron) also markedly potentiates the toxicity of adenine arabinonucleoside and of cordycepin (3'-deoxyadenosine) against HeLa cells and against the production of HSV in those cells. Cordycepin alone (10 micron) does not inhibit HSV replication whereas in combination with 10 micron EHNA there is a greater than 99% inhibition of virus production. Under these conditions, RNA synthesis is inhibited by more than 80% whereas protein and DNA synthesis are inhibited to a lesser extent; in this system, virtually all of the DNA synthesis in infected cells is that of host DNA. Thus, EHNA appears to affect the synthesis of HSV DNA specifically in two different ways, depending on whether it is used alone or in the presence of cordycepin.
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PMID:Erythro-9-(2-hydroxy-3-nonyl)adenine as a specific inhibitor of herpes simplex virus replication in the presence and absence of adenosine analogues. 21 93

The human lymphoblast line WI-L2 is subject to growth inhibition by a combination of the adenosine deaminase (ADA; adenosine aminohydrolase, EC 3.5.4.4.) inhibitor erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) and adenosine. Although adenosine-induced pyrimidine starvation appears to contribute to this effect, uridine only partially reverses adenosine toxicity in WI-L2 and not at all in strain 107, an adenosine kinase-(ATP:adenosine 5'-phosphotransferase, EC 2.7.1.20) deficient derivative of WI-L2. Treatment of both cell lines with EHNA and adenosine leads to striking elevations in intracellular S-adenosyl-L-homocysteine (AdoHcy), a potent inhibitor of S-adenosyl-L-methionine (AdoMet)-dependent methylation reactions. The methylation in vivo of both DNA and RNA is inhibited by concentrations of EHNA and adenosine that elevate intracellular AdoHcy. Addition of 100 muM L-homocysteine thiolactone to cells treated with EHNA and adenosine enhances adenosine toxicity and further elevates AdoHcy to levels approximately 60-fold higher than those obtained in the absence of this amino acid, presumably by combining with adenosine to form AdoHcy in a reaction catalyzed by S-adenosylhomocysteine hydrolase (EC 3.3.1.1). In the adenosine kinase-deficient strain 107, a combination of ADA inhibition and L-homocysteine thiolactone markedly increases intracellular AdoHcy and inhibits growth even in the absence of exogenous adenosine. These results demonstrate a form of toxicity from endogenously produced adenosine and support the view that AdoHcy, by inhibiting methylation, is a mediator of uridine-resistant adenosine toxicity in these human lymphoblast lines. Furthermore, they suggest that AdoHcy may play a role in the pathogenesis of the severe combined immunodeficiency disease found in most children with heritable ADA deficiency.
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PMID:S-adenosylhomocysteine toxicity in normal and adenosine kinase-deficient lymphoblasts of human origin. 22 26

The release and metabolism of adenosine was examined using rat fat cells in which the nucleotide pool has been labeled by incubation with radioactive adenine. The accumulation of adenosine in the medium was near maximal at the start of the incubation and increased only slightly thereafter. Adenosine was rapidly deaminated to inosine and subsequently oxidized to uric acid. In the presence of allopurinol, and inhibitor of xanthine dehydrogenase, hypoxanthine accumulated in the medium as the end-product of adenosine catabolism. Adenosine accumulated in the medium only if fat cells were incubated in the presence of erythro-9-(2-hydroxy-3-nonyl)adenine, an inhibitor of adenosine deaminase. Even in the presence of this inhibitor there was no acceleration of adenosine release by norepinephrine in the presence of theophylline. However, there was an increase in labeled intracellular AMP accumulation by norepinephrine plus theophylline. The increase in labeled AMP correlated with the final free fatty acid to albumin ratio suggesting that the rise in AMP was related to an accumulation of intracellular free fatty acids. The addition of sodium oleate to the medium mimicked the effect of norepinephrine plus theophylline on the accumulation of labeled AMP. These results indicate that AMP rather than adenosine accumulates in isolated fat cells during incubation with lipolytic agents.
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PMID:Effect of lipolytic agents on adenosine and AMP formation by fat cells. 22 45

Since extracellular adenosine is a physiologically important regulator of adenylate cyclase and cell function in various mammalian tissues, we have examined the effect of adenosine on histamine release from human basophils. Adenosine inhibited IgE-mediated histamine release by its ability to increase leukocyte cyclic AMP levels; the same concentrations of adenosine which inhibited histamine release increased the cyclic AMP level of mixed leukocytes. Inhibition of histamine release was also observed with an adenosine deaminase (ADA) inhibitor [erythro-9-(2-hydroxy-3-nonyl)-adenine: EHNA] in the presence of autologous serum. We suggest that the adenosine-ADA system normally modulates histamine release and that this contributes to the severe combined immune deficiency (SCID) associated with a lack of ADA.
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PMID:Adenosine-adenosine deaminase modulation of histamine release from human basophils in vitro. 22 78


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