Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Purified inside-out vesicles from human erythrocytes were used to investigate the active transport of oxidized glutathione (GSSG). Incubation of vesicles and GSSG in the presence of ATP resulted in the transport of GSSG into the vesicles. When vesicles were incubated with reduced glutathione (GSH), no transport was observed. At GSSG concentrations of less than 5 mM, transport was linear up to 4 hr at 37 degrees C. A Lineweaver-Burk plot of the transport rate as a function of GSSG concentration was biphasic and gave apparent Km values of 0.1 and 7.1 mM. The Km for ATP . Mg in this transport process was 0.63 mM at a GSSG concentration of 20 microM and 1.25 mM at a GSSG concentration of 5 mM. The transport rate at low GSSG concentrations was inhibited by CTP or UTP, which acted as competitive inhibitors of ATP; Ki=0.51 mM. This inhibition may account for the high erythrocyte GSH levels observed in pyrimidine-5'-nucleotidase deficiency, a disorder in which erythrocytic levels of CTP and UTP are elevated.
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PMID:Glutathione transport by inside-out vesicles from human erythrocytes. 693 50

An IMP-hydrolysing enzyme was purified to homogeneity from yeast extract. It was a soluble protein with an apparent molecular mass of 220 kDa, with a subunit molecular mass of 55 kDa. It was highly specific for IMP, and there was virtually no detectable activity with the other purine and pyrimidine nucleotides tested, including AMP and dIMP. The enzyme had a pH optimum of 6.0-6.5. Its activity was absolutely dependent on bivalent metal salts: Mg2+ was most potent, followed by Co2+ and Mn2+. The velocity/substrate-concentration plot of the enzyme was slightly sigmoidal (h = 1.7) and the s0.5 was 0.4 mM. ATP stimulated the enzyme by decreasing both h and s0.5. Diadenosine tetraphosphate stimulated the enzyme as effectively as ATP. Although the properties of the enzyme are similar to those of the IMP/GMP 5'-nucleotidase identified in various animals [Itoh (1993) Comp. Biochem. Physiol. 105B, 13-19], the substrate specificity of the former was much more strict than the latter.
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PMID:Purification and some properties of an IMP-specific 5'-nucleotidase from yeast. 814 71

1. A search for nucleoside phosphotransferase activity in Bacillus cereus led to the following results: (i) The phosphotransferase activity was associated with a membrane bound 5'-nucleotidase. (ii) The enzyme phosphorylates both purine and pyrimidine nucleosides as well as 2',3'-dideoxyinosine. (iii) The enzyme was inhibited by adenylic nucleotide di- and triphosphates, and its nucleotidase activity was increased in the presence of inosine as phosphate acceptor. 2. Bacterial and vertebrate 5'-nucleotidases with phosphotransferase activity differ for several characteristics, such as cellular location, substrate specificity, magnesium requirement and regulation.
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PMID:Membrane-bound 5'-nucleotidase/nucleoside phosphotransferase from Bacillus cereus. 828 31

The antiviral activity of the purine dideoxynucleosides 2',3'-dideoxyadenosine (ddA) and 2',3'-dideoxyinosine (ddI) is dependent on their conversion into ddA triphosphate in vivo. 5-Amino-4-imidazolecarboxamide riboside (AICA riboside), a natural metabolite in purine biosynthetic pathways, is converted into IMP, a substrate for the biosynthesis of adenine and guanine nucleotides, and enhances the intracellular purine nucleotide pools. Because IMP also serves as a phosphate donor in the anabolic phosphorylation of ddI (and ddA) into ddI monophosphate by the cytosolic enzyme 5'-nucleotidase, we investigated the effects of AICA riboside on the phosphorylation and antiretroviral activity of these purine nucleoside analogs. At an AICA riboside concentration of 0.5 mM, there was a approximately 2-fold increase in the intracellular ATP and GTP levels, whereas a nearly 8-fold increase was observed for the phosphorylation of ddA (or ddI). A marked reduction in intracellular pools of the pyrimidine nucleotides CTP and UTP was observed in AICA riboside-treated cells and inhibited cell proliferation. However, this growth inhibition was prevented by the addition of uridine to the cultures. Cells pretreated with AICA riboside and ddI were less susceptible to human immunodeficiency virus (HIV) infection and synthesized reduced levels of HIV proviral DNA. A 10-fold potentiation of the effectiveness of ddI against both wild-type HIV (HIVIIIB) and a ddI-resistant variant HIV was observed in the presence of 0.5 mM AICA riboside. These results show that AICA riboside modulates the anabolism and antiviral activity of ddI, and they have implications for possible therapies with dideoxynucleosides.
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PMID:5-Amino-4-imidazolecarboxamide riboside potentiates the metabolism and anti-human immunodeficiency virus activity of 2',3'-dideoxyinosine. 834 Dec 76

An 11-year-old girl had marked haemolytic anaemia since the first year of life. Physical examination revealed scleral and cutaneous icterus and slight splenomegaly. Haemoglobin concentration was reduced to 9.5 g/dl, while platelet count and bilirubin concentration were increased (350,000/microliter and 2.2 mg/dl, respectively). The erythrocytes showed marked basophilic stippling, its extent typical of pyrimidine-5'-nucleotidase deficiency. The enzyme activity in the erythrocytes was 15% of normal. Deficiency of this enzyme, inherited as an autosomal recessive, is probably one of the most common erythrocyte enzyme deficiencies causing haemolytic anaemia. It brings about the intracellular accumulation of pyrimidine nucleotides which via secondary metabolic changes causes an accelerated destruction of erythrocytes. There is no known causative treatment: splenectomy is ineffective against the anaemia.
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PMID:[Pyrimidine 5'-nucleotidase deficiency as the congenital cause of nonspherocytic hemolytic anemia]. 837 97

1. Using the incorporation of [methyl-3H]thymidine as a proliferation marker, the effects of various nucleosides and nucleotides on endothelial LLC-MK2 cells were studied. We found that ATP, ADP, AMP and adenosine in concentrations of 10 microM or higher stimulate the proliferation of these cells. 2. Inhibition of ecto-ATPase (EC 3.6.1.15), 5'-nucleotidase (EC 3.1.3.5) or alkaline phosphatase (EC 3.1.3.1) significantly diminished the stimulatory effect of ATP, indicating that the effect is primarily caused by adenosine and not by adenine nucleotides. Also, the effect depends only on extracellular nucleosides, since inhibition of nucleoside uptake by dipyridamole has no influence on proliferation. 3. Other purine nucleotides and nucleosides (ITP, GTP, inosine and guanosine) also stimulate cell proliferation, while pyrimidine nucleotides and nucleosides (CTP, UTP, cytidine and uridine) inhibit proliferation. Furthermore, the simultaneous presence of adenosine and any of the other purine nucleosides is not entirely additive in its effect on cell proliferation. At the same time any pyrimidine nucleoside, when added together with adenosine, has the same inhibitory effect as the pyrimidine nucleoside alone. 4. Apparently these proliferative effects are neither caused by any pharmacologically known P1-purinoceptor, nor are they mediated by cyclic AMP, cyclic GMP, or D-myo-inositol 1,4,5-trisphosphate as second messenger, nor by extracellular Ca2+. 5. Therefore, we conclude that various purine and pyrimidine nucleosides can influence the proliferation of LLC-MK2 cells by acting on putative purinergic and pyrimidinergic receptors not previously described.
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PMID:Regulation of proliferation of LLC-MK2 cells by nucleosides and nucleotides: the role of ecto-enzymes. 868

Among the biological exposure indices of lead, lead in plasma was the most direct indicator of current exposure. Lead mobilized into plasma as well as in urine could be used as an indicator of the internal dose of lead. The ratio of non-treated to restored activity of delta-aminolevulinic acid dehydratase (ALA-D) was a more specific index than ALA-D activity itself at low levels of lead exposure, excluding the familial or genetic variation in the activity. The methods using HPLC for determining heme intermediate improved the evaluation of the lead effect: delta-aminolevulinic acid in plasma, blood, and urine (ALA-P, ALA-B, and ALA-U), coproporphyrin in urine, and zinc protoporphyrin in blood (ZP). ROC (Receiver operating characteristic) curve analyses indicated that the diagnostic values for lead exposure decreased in the order ALA-D ratio > ALA-D activity = ALA-P > ALA-U = ZP. Pyrimidine 5'-nucleotidase activity or pyrimidine nucleotide concentrations in blood was also useful for the monitoring or diagnosis of lead intoxication. Using the HPLC method with inclusion compounds in the mobile phase, hippuric acid, methylhippuric acids, mandelic acid and phenylglyoxylic acid could be simultaneously determined in the urine of workers exposed to a mixture of toluene, xylenes, and ethylbenzene. The correction of the urinary metabolite concentration for specific gravity or creatinine allowed the more specific evaluation of the solvent exposure. In the biological monitoring of chlorinated hydrocarbons such as trichloroethylene, prolonged excretion of the metabolites resulted in a bias between metabolite concentrations and TWA levels of the solvent in a day. The background levels of 2,5-hexanedione (HD) were affected by acid hydrolysis conditions, age, sex and lipid metabolism. Substances hydrolyzed to HD in urine from non-exposed subjects were different from HD detected in the workers exposed to n-hexane. Urinary concentrations of N-acetyl-S-(N-methylcarbamoyl) cysteine (AMCC) served as an index of the average exposure to N, N-dimethylformamide during several preceding work days and may indicate the internal dose, while N-methylformamide may be an index of daily exposure. A simple and rapid method for the determination of urinary alkoxyacetic acids was recently developed for the biological monitoring of workers exposed to glycolethers and their acetates. Urinary butoxy acetic acid (free plus conjugated ones) could be simply determined by gaschromatography after acid hydrolysis of urine. The urinary acetone or methanol concentration determined by the head space technique was also useful for the biological monitoring of workers exposed to isopropanol and/or acetone, or methanol, respectively. Evaluation of exposure to the solvents described above could be carried out by comparing the urinary metabolite concentrations with reference values and the biological exposure index values which were defined as the urinary metabolite concentration corresponding to the threshold value for each solvent.
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PMID:[Studies on the evaluation of exposure to industrial chemicals]. 868 99

Four unrelated patients are described with a syndrome that included developmental delay, seizures, ataxia, recurrent infections, severe language deficit, and an unusual behavioral phenotype characterized by hyperactivity, short attention span, and poor social interaction. These manifestations appeared within the first few years of life. Each patient displayed abnormalities on EEG. No unusual metabolites were found in plasma or urine, and metabolic testing was normal except for persistent hypouricosuria. Investigation of purine and pyrimidine metabolism in cultured fibroblasts derived from these patients showed normal incorporation of purine bases into nucleotides but decreased incorporation of uridine. De novo synthesis of purines and cellular phosphoribosyl pyrophosphate content also were moderately decreased. The distribution of incorporated purines and pyrimidines did not reveal a pattern suggestive of a deficient enzyme activity. Assay of individual enzymes in fibroblast lysates showed no deficiencies. However, the activity of cytosolic 5'-nucleotidase was elevated 6- to 10-fold. Based on the possibility that the observed increased catabolic activity and decreased pyrimidine salvage might be causing a deficiency of pyrimidine nucleotides, the patients were treated with oral pyrimidine nucleoside or nucleotide compounds. All patients showed remarkable improvement in speech and behavior as well as decreased seizure activity and frequency of infections. A double-blind placebo trial was undertaken to ascertain the efficacy of this supplementation regimen. Upon replacement of the supplements with placebo, all patients showed rapid regression to their pretreatment states. These observations suggest that increased nucleotide catabolism is related to the symptoms of these patients, and that the effects of this increased catabolism are reversed by administration of uridine.
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PMID:Developmental disorder associated with increased cellular nucleotidase activity. 932 56

High energy phosphate levels fall rapidly during cardiac ischemia and recover slowly (more than one week) during reperfusion. The slow recovery of ATP may reflect a lack of purine metabolic precursors and/or increased activity of purine catabolic enzymes such as 5'-nucleotidase (5'-NT, EC 3.1.3.5) and adenosine deaminase (ADA, EC 3.5.4.4). The activity of enzymes involved in both the catabolism of ATP precursors (5-NT and ADA) and the restoration of ATP from slow synthetic pathways [adenosine kinase (AK, EC 2.7.1.20), adenine phosphoribosyl transferase (APRT, EC 2.4.2.7) and hypoxanthine phosphoribosyl transferase (HPRT, EC 2.4.2.8)] may directly affect the rate of ATP recovery. Strategies to enhance recovery will depend on the relative activity of these enzymes following ischemia. Their activity in different species and their response to ischemia are not well characterized. Hence, rapid assay methods for these enzymes would facilitate detailed time course studies of their activities in postischemic myocardium. We modified a single ion-exchange column chromatographic method using DEAE-Sephadex to determine the products of incubation of 5'-NT, AK, APRT and HPRT with their respective substrates. The uniformity of the final product measurement procedure for all assays permits the activities of the four enzymes to be rapidly determined in a single tissue sample and facilitates the study of a large number of samples. This technique should also be useful for enzymes of the pyrimidine metabolic pathway.
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PMID:Ion-exchange column chromatographic method for assaying purine metabolic pathway enzymes. 961 62

Substrate and product specificity studies were used to develop inhibitors of the cytosolic 5'-nucleotidase I (c-N-I) from myocardium. As measured by Vmax/Km, c-N-I preferred pyrimidine 2'-deoxyribonucleotides as substrates with thymidine monophosphate (TMP) being the most efficient. In product inhibition studies, thymidine inhibited noncompetitively and inorganic phosphate inhibited competitively, consistent with an ordered release of nucleoside prior to phosphate. Mirroring nucleotide substrate specificities, pyrimidine nucleosides were more potent product inhibitors than purine nucleosides. Thus, pyrimidine nucleotide and nucleoside analogues were developed as inhibitors. Phosphonate analogues of TMP were synthesized by a novel method. The most potent was the 5'-phosphonate of 3'-deoxythymidine (ddT) (apparent Ki value of 63 nM). In addition, pyrimidine nucleoside analogues were inhibitors with 5-ethynyl-2',3'-dideoxyuridine being the most potent (apparent Ki value of 3.7 microM). The most potent nucleotide and nucleoside inhibitor were both greater than 1000-fold more potent inhibiting c-N-I than the cytosolic 5'-nucleotidase II. The nucleoside analogue was also greater than 1000-fold more potent against c-N-I than the membrane ecto-5'-nucleotidase (e-N). Because the phosphonate analogues measurably inhibited e-N (apparent Ki values of 6-12 microM), the selectivity of the phosphonates for c-N-I versus e-N was less (40-200-fold). Because of the high selectivity for c-N-I versus both of the other 5'-nucleotidases, the nucleoside inhibitors of c-N-I may be useful biochemical tools in discerning the role that c-N-I plays in generating adenosine within myocardium.
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PMID:Nucleotide and nucleoside analogues as inhibitors of cytosolic 5'-nucleotidase I from heart. 963 49


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