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:3.1.3.5 (5'-nucleotidase)
3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inhibition of 3':5'-cyclic-AMP-5'-nucleotidohydrolase (EC 3.1.4.17) type II (cAMP-phosphodiesterase) by sodium molybdate was studied: While determination of inorganic phosphate and 5'-ribonucleotide phosphohydrolase (5'-nucleotidase) (EC 3.1.3.5) activity was not disturbed by sodium molybdate in concentrations up to 10 mM, cAMP-phosphodiesterase was inhibited by millimolar concentrations of molybdate. The half maximal effect was observed at about 2 mM sodium molybdate (0.75 mM cAMP in the assay).
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PMID:Inhibition of cAMP-phosphodiesterase by molybdate. 303 26

5'-Nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) of bovine milk fat globules can be solubilized by deoxycholate from either isolated globule membranes or washed cream. The solubilized and membrane-bound enzymes exhibit similar Km values and are inhibited by concanavalin A by an apparent noncompetitive process. The soluble enzyme shows positive cooperativity for the inhibition (Hill coefficient of 2) at 37 degrees C, but the membrane enzyme exhibits essentially no cooperation effect. At lower temperatures (5 or 20 degrees C) the cooperative effect in the inhibition of the soluble enzyme is lost. Colchicine and cytochalasin D failed to induce cooperativity of the concanavalin A inhibition of the membrane enzyme, but induction cooperativity occurred when membranes were extracted with glycine/EDTA/mercaptoethanol, releasing a major protein component with a polypeptide molecular weight of 155 000. We suggest that the interaction of this component with the membrane imposes restraints on the behavior of the nucleotidase which are reflected in the cooperativity of the inhibition of the enzyme by concanavalin A.
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PMID:Cooperativity of the concanavalin A inhibition of bovine milk fat globule membrane 5'-nucleotidase. Response to extraction of nucleotidase and of putative cytoplasmic surface coat components. 624 89

The growth of cultured leukemic T-lymphocytes is readily inhibited by deoxynucleosides, particularly thymidine, deoxyguanosine, and deoxyadenosine. By contrast, Epstein-Barr virus-transformed B-lymphocytes are relatively resistant to deoxynucleosides. Growth inhibition correlates with the development of high deoxyribonucleoside triphosphate pools following exposure to deoxynucleosides. Leukemic T-lymphocytes are deficient in ecto-5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) activity, and it has been postulated that deficiency of this enzyme decreases the capacity of these cells to degrade deoxyribonucleotides, rendering them sensitive to deoxynucleosides. We find that the sensitivity of cultured null-type leukemic lymphocytes to growth inhibition of deoxynucleosides is similar to that of T-cells. However, the null cells contain normal levels of ecto-5'-nucleotidase. We infer that ecto-5'-nucleotidase deficiency does not have a central role in determining the deoxynucleoside sensitivity of leukemic lymphocytes.
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PMID:Sensitivity of leukemic human null lymphocytes to deoxynucleosides. 625 63

A 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) was highly purified from rat liver. The preparation appeared homogeneous on the criteria of disc-gel electrophoresis. A pH optimum at about 6.5 was observed for all substrates tested. The activity of this enzyme was absolutely dependent on the presence of various bivalent metal salts. The highest V value was attained with MgCl2 and the concentration at half-enzyme saturation was lowest with MnCl2. The enzyme had markedly higher affinities for IMP, dIMP, GMP and dGMP than the other 5'-mononucleotides, although V values for all the substrates tested were in the same order of magnitude. The activity of this enzyme was stimulated by various alkali metal salts, some carboxylic acids and adenine nucleotides. When AMP was used as substrate, the substrate-velocity plot was sigmoidal and NaCl, Tris-maleate and ATP stimulated the enzyme by decreasing the sigmoidicity of the plot. When IMP was used as substrate, the substrate-velocity plot was hyperbolic and these three activators stimulated the enzyme by increasing the V and decreasing the Km value. Some of these results provided consistent evidence for the identity of this enzyme and the cytosol 5'-nucleotidase, the presence of which had been reported in crude preparations from rat liver.
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PMID:Purification and some properties of cytosol 5'-nucleotidase from rat liver. 626 Feb 3

5'-Nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) activity was stimulated by increasing the concentration of Tris over the range of 1--100 mM. Significant differences were found when the kinetic parameters of the enzyme determined in Tris were compared to those determined in glycine. These data suggest that Tris interacts with 5'-nucleotidase and is therefore unsuitable for use in the assay of the enzyme.
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PMID:The effect of tris(hydroxymethyl) aminomethane on membrane bound 5'nucleotidase from swine aortic smooth muscle. 626 Feb 8

In the physiological range of the adenylate energy charge in liver (0.7-0.9), th rate of AMP-hydrolysis catalysed by rat liver cytosol 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) increased sharply with decreasing energy charge. In addition, a decrease in the concentration of Pi caused marked acceleration of the AMP-hydrolysing activity over the physiological range of adenylate energy charge. These responses seem to serve to protect the cells against a metabolic stress which could result from sudden utilization of ATP by removal of AMP. The AMP-hydrolysing activity of this enzyme decreased sharply as the size of the adenine nucleotide pool decreased in the physiological range. This effect may be a self-limiting response to prevent excess depletion of the pool. IMP-hydrolysing activity of this enzyme increased with increasing adenylate energy charge. But no marked response to its variation within the physiological range was observed. On the basis of the data obtained in this study, the IMP-hydrolysing activity of the cytosol 5'-nucleotidase in rat liver cells seems to be comparable to that of AMP deaminase reaction, but the AMP-hydrolysing activity was estimated to be less than 10% of AMP deaminase reaction at energy charge value of about 0.7. This strongly suggests that the AMP leads to IMP leads to inosine pathway is more significant that the AMP leads to adenosine leads to inosine pathway in rat liver.
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PMID:Regulation of cytosol 5'-nucleotidase by adenylate energy charge. 626 62

A previously unknown 5'nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) (5'-Nase) specific for orotidine 5'-monophosphate (OMP) hs been discovered. This enzyme orotidine 5'-monophosphate phosphohydrolase (OMPase), was isolated from mouse liver microsomes as a separate entity from the nonspecific 5'-Nase. OMPase was partially purified and is shown to cleave OMP to orotidine and inorganic phosphate. The enzyme has negligible activity towards UMP, CMP, dTMP, AMP, IMP, GMP, XMP, 6-azauridine 5'-monophosphate, 1-beta-D-ribofuranosylbarbituric acid 5'-monophosphate (BMF), 2'-UMP, 3'-UMP, 2'-AMP, 3'-AMP, ribose 5-phosphate and beta-glycerophosphate, all of which--with the exception of the 2' or 3' monophosphates, ribose 5'-phosphate, and beta-glycerophosphate--are substrates for 5'-Nase. Both enzymes are inhibited by NaF, but only OMPase is inhibited by SF reagents. OMPase is not inhibited by orotidine, orotate, BMP, concanavalin A, or tetramisole (an alkaline phosphatase inhibitor). OMPase had a Mr 53,000, Km value of 1 mM for OMP, and Vmax value of 49 nmol/min . mg of protein at the present stage of purification. OMPase activity has also been detected in various mammalian tissues including normal human tissues, human tumor xenografts, lymphocytes, and rat liver. OMPase may be responsible, in part, for the low levels of intracellular "free" OMP and for orotidine accumulation in cells treated with 6-azauridine and patients suffering from aortic aciduria.
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PMID:Isolation and partial characterization of a 5'-nucleotidase specific for orotidine-5'-monophosphate. 628 Jan 63

The activity of 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) was examined in membrane fractions isolated by hypotonic shock-LiBr treatment (fraction HL) and sucrose gradient separation (fraction S) of rat ventricle homogenate. The enzyme activity in these two fractions differed significantly in several respects. In fraction HL, 5'-nucleotidase had a high affinity for AMP (Km 35 microM), and ATP was a potent competitive inhibitor. In contrast, the 5'-nucleotidase displayed by fraction S showed a low substrate affinity (Km 130 microM) and less sensitivity to ATP. Treatment of membranes with trypsin and neuraminidase markedly stimulated 5'-nucleotidase in fraction HL, whereas only a modest effect was observed in fraction S. Exposure of the membranes to Triton X-100 resulted in a 60% and 10% increase in the enzyme activity in fractions HL and S, respectively. The characteristic activity ratios of 5'-nucleotidase at 200 microM relative to 50 microM AMP in fractions HL and S were modified by alamethicin in an opposite way and became identical. Although concanavalin A almost completely inhibited the 5'-nucleotidase activity in both membrane preparations at a concentration of 2 microM, Hill plots of the data on concanavalin A inhibition revealed a coefficient of 2.2 for fraction S and 1.1 for fraction HL. The differences in 5'-nucleotidase activity of the two membrane fractions are considered to be due to differences in the orientation of the vesicles of the sarcolemmal preparations. These results suggest that two distinct catalytic sites for 5'-nucleotidase are present at the intra- and extracellular surface of the rat heart sarcolemma.
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PMID:Properties of 5'-nucleotidase in rat heart sarcolemma. 630 58

The effect of adenosine on the metabolism of prelabeled adenine nucleotides was investigated in isolated hepatocytes. Adenosine caused an approximately equal to 2-fold increase in the ATP content of the cells. This effect was in part counteracted by an increased rate of adenine nucleotide catabolism that could be explained by a stimulation of both AMP deaminase (AMP aminohydrolase, EC 3.5.4.6) and the cytoplasmic 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) because of the increased concentration of ATP. The unexpected finding that labeled adenosine was formed immediately after the addition of the unlabeled nucleoside could be explained by the trapping effect of adenosine. An accumulation of labeled adenosine was observed also in the presence of 5-iodotubercidin, a potent inhibitor of adenosine kinase (ATP:adenosine 5'-phosphotransferase, EC 2.7.1.20). Under these conditions, there was a decrease in the concentration of ATP in the cell and a 2- to 3-fold increase in the rate of formation of allantoin. This formation of adenosine was only slightly decreased by inhibition of the membranous 5'-nucleotidase; it led to the accumulation of S-adenosylhomocysteine in the presence of coformycin and an excess of L-homocysteine. It was concluded that, under basal conditions, the cytoplasmic 5'-nucleotidase present in the liver cell continuously produces adenosine, which is immediately reconverted into AMP by adenosine kinase, without giving rise to allantoin. This futile cycle between AMP and adenosine amounts to at least 20 nmol/min per g of liver and, thus, exceeds the basic rate of allantoin formation.
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PMID:Evidence for a substrate cycle between AMP and adenosine in isolated hepatocytes. 630 84

5'-Nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) occurs in bull seminal plasma in multiple forms. The heterogeneity does not reflect the existence of true isoenzymes, but is due to the association of the enzyme with particulate material and to molecular aggregation phenomena. Addition of detergents to native bull seminal plasma prevents molecular aggregation, solubilizes the particulate form of the enzyme, and results in the appearance of a single molecular form of the enzyme. Enzyme purification can be achieved after three chromatographic steps which involve negative adsorption of 5'-nucleotidase activity on DEAE-Sephadex A-50 followed by two affinity chromatographies on concanavalin A-Sepharose 4B and ADP-agarose. The enzyme appears to be a dimeric glycoprotein. Some properties of the enzyme, including substrate specificity and the effects of hydrogen ion concentration and of various divalent cations, are reported.
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PMID:5'-nucleotidase from bull seminal plasma. 631 64


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