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)

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

Human red cell pyrimidine-5'-nucleotidase (EC 3.1.3.5) was partially purified from the blood of normal subjects by ion-exchange and affinity chromatography. Red cells were lysed in 50 mmol/l Tris-Cl buffer at pH 7.5 containing 1.0 mmol/l dithiothreitol and 0.5 mmol/l EDTA. The lysate was centrifuged and introduced onto a column of Sephadex A-50. After washing, the pyrimidine-5'-nucleotidase activity was eluted from the column with a NaCl gradient from 0 to 200 mmol/l in Tris buffer at pH 7.5. The pyrimidine-5'-nucleotidase was then desalted on Sephadex G-25 and introduced onto a UDP agarose column with a Tris buffer at pH 6.5 containing 150 mmol/l NaCl. This partial purification resulted in an approximately 80,000-fold increase in enzyme concentration. The Km for the partially purified enzyme was 0.32 mmol/l for UMP, 0.16 mmol/l for CMP and 0.11 mmol/l for OMP with a pH maximum of 7.5. This partially purified pyrimidine-5'-nucleotidase was then dialyzed in 50 mmol/l Tris-Cl buffer at pH 7.5 with 0.01 mmol/l CaCl2 and NaCl against 2 X 10(-3) mol/l 1,10-phenanthroline for 24 h at 4 degrees C. This incubation resulted in 73% decrease in enzyme activity which could be restored by the addition of zinc into the mixture, but not by the addition of other divalent metal ions.
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PMID:Partial purification and zinc dependence of human red cell pyrimidine-5'-nucleotidase. 631 32

The developmental pattern of the myelin-associated 5'-nucleotidase and its regulation by L-3,3',5,-triiodothyronine (T3) have been demonstrated in a culture system of cells dissociated from embryonic mouse brain. Hypothyroid calf serum containing low levels of T3 (31 ng/100 ml), and thyroxine, T4 (less than 1 microgram/ml), was used in the culture medium in place of normal calf serum (T3, 103 ng/100ml; T4, 5.7 micrograms/ml) to render the cultures responsive to exogenously added T3. By means of T3 supplementation, the lower levels of enzyme activity observed in the cultures grown in the presence of hypothyroid calf-serum containing medium could be restored to a considerable extent although not completely to normal values. Half-maximal stimulatory effect was obtained at 3.9 X 10(-8)M T3 concentration. Among the various substrates tested, 5'-AMP, 5'-UMP and 5'-CMP were equally good, while 5'-GMP yielded approximately half the activity.
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PMID:Investigations on myelinogenesis in vitro: regulation of 5'-nucleotidase activity by thyroid hormone in cultures of dissociated cells from embryonic mouse brain. 633 Mar 77

A major role of the Golgi apparatus in liver is the terminal glycosylation of secreted serum proteins and of plasma membrane glycoproteins. Galactosyltransferase is a membrane-bound Golgi enzyme that transfers galactose directly from uridine diphosphogalactose (UDP-Gal) to terminal N-acetylglucosamine groups of N-asparagine-linked glycoproteins during secretion. Sialytransferase then transfers sialic acid from cytidine monophosphosialic acid (CMP-NAN) to the newly added terminal galactose of the glycoprotein. In the cell, the transfer reaction must occur on the lumen side of the Golgi membrane. UDP-Gal is synthesized mainly in the cytoplasm and CMP-NAN is synthesized in the nucleus in liver. An important question for understanding the mechanism is, how do these nucleotide sugars gain access to the transferases? A second question involves uridine diphosphate (UDP), a highly inhibitory product of galactosyltransferase. How is UDP removed from the lumen of the Golgi fast enough to prevent product inhibition of the galactosyltransferase? We have shown that isolated Golgi, although vesiculated, retains its original orientation. The vesicles are oriented with greater than 90% of both galactosyltransferase and sialyl-transferase on the luminal side of the vesicles. Using intact vesicles, we can show that UDP-Gal is taken up via a saturable carrier system present in the Golgi membrane. During galactosylation in vitro, UDP formed in the lumen of Golgi vesicles is rapidly converted to UMP by a nucleoside diphosphatase in the lumen. Uridine monophosphate, which is much less inhibitory to the galactosyltransferase than UDP, is then transported out of the lumen by a second carrier and is broken down further to uridine by 5'-nucleotidase on the cytoplasmic side of the Golgi vesicles. The transport of nucleotides appears unique to the Golgi membranes, since neither rough endoplasmic reticulum nor plasma membrane vesicles from rat liver accumulate these nucleotides.
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PMID:Mechanism of glycosylation in the Golgi apparatus. 634 57

Induction studies on pyrimidine metabolizing enzymes in E. coli B have shown that the enzymes fall into three distinct groups according to their induction pattern. a) Cytidine deaminase and uridine phosphorylase, are induced by cytidine, CMP and adenosine; no induction was observed with uridine and AMP; b) thymidine phosphorylase is induced by cytidine, adenosine, all deoxyribonucleosides, CMP, deoxyribonucleotides, deoxyribose and deoxyribose-1-phosphate; c) uridine-cytidine kinase, uracil phosphoribosyltransferase, 5'-nucleotidase, thymidine kinase, are uninducible enzymes. Simultaneous addition of cytidine and glucose partially overcomes the cytidine deaminase and uridine phosphorylase induction. Cytidine deaminase reaches its maximum activity levels, in E. coli growing cells in presence of cytidine, two hours before the uridine phosphorylase activity. Maximum glucose repression of cytidine deaminase and uridine phosphorylase was obtained in correspondence of maximum cytidine induction.
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PMID:Induction of pyrimidine nucleoside metabolizing enzymes in E. coli B. 636 Sep 49

Six 5'-(steroid-21-phosphoryl)-1-(beta-D-arabinofuranosyl)cytosines have been prepared and evaluated against L1210 lymphoid leukemia in culture and in mice (C3D2F1/J). These include the ara-C conjugates of 11-deoxycorticosterone (5a), corticosterone (5b), cortexolone (5c), fludrocortisone (5d), 6 alpha-methylprednisolone (5e), and dexamethasone (5f). When the optimum dosage of ara-C [38 (mumol/kg)/day X 5] was given to mice bearing L1210, the ILS value found was 89%. A simple mixture of each steroid and ara-C gave ILS values that were on the whole significantly less than that of the parent nucleoside. However, of six conjugates, all but two (5d and 5f) were more active than ara-C at their optimal doses. Both corticosterone- (5b) and cortexolone-p-ara-C (5c) were especially effective at the respective optimal doses of 76.7 and 115 (mumol/kg)/day X 5. These gave ILS values of 200% each. All of the conjugates were demonstrated to be enzymatically hydrolyzed to the corresponding steroid and ara-CMP, and the latter was further shown to be hydrolyzed to ara-C by phosphodiesterase I, 5'-nucleotidase, and acid phosphatase. However, they were shown to be resistant to hydrolysis by alkaline phosphatase.
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PMID:Nucleoside conjugates as potential antitumor agents. 3. Synthesis and antitumor activity of 1-(beta-D-arabinofuranosyl)cytosine conjugates of corticosteroids. 745 87

Soluble low Km 5'-nucleotidases have been purified from human cultured T- and B-lymphoblasts to compare their properties and to examine the mechanism of different rates of nucleotide dephosphorylation. The enzyme from B-lymphoblasts (MGL-8) was 4385-fold purified with a specific activity of 114 mumol/min/mg, while the enzyme from T-lymphoblasts (CEM, MOLT-4) was 4355-fold purified with a specific activity of 35 mumol/min/mg. The activity of both enzymes have an absolute requirement for Mg++. The B-cell enzyme has maximum activity with Mg2+ > Mn2+ > Co2+, while the T-cell enzyme had maximum activity with Co2+ > Mn2+ > Mg2+. The optimum activity was at pH 7.4-9.0 for the B-cell enzyme and pH 9.0 for the T-cell enzyme. Substrate specificity was the same for both enzymes with the following relative Vmax values: CMP > UMP > dUMP > dCMP > dAMP > IMP > GMP > dIMP > dGMP. The Km values for AMP and IMP were 12 and 25 microM for the B-cell enzyme, and 7.0 and 12 microM for the T-cell enzyme. ATP and ADP are competitive inhibitors of these enzymes with apparent Ki values of 100 and 20 microM for the B-cell enzyme, and 44 microM and 8 microM for the T-cell enzyme, respectively. The apparent molecular mass by gel filtration column chromatography is 145 kD for the B-cell enzyme and 72 kDa for the T-cell enzyme. The subunit molecular masses by Western blots are 69.2 kD for both enzymes. These properties suggest that the B-lymphoblast enzyme is identical or similar to the enzyme from human placenta. However, the T-cell enzyme has some different properties. We conclude that these differences plus a lower content of low Km 5'-nucleotidase in T-cells may account for the decreased ability of T-lymphoblasts to dephosphorylate nucleotides and may contribute to the selective cytotoxicity of deoxyribonucleosides for T-lymphoblasts as compared to B-lymphoblasts.
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PMID:Altered properties of human T-lymphoblast soluble low Km 5'-nucleotidase: comparison with B-lymphoblast enzyme. 845 Jun 71

Human seminal plasma contains two enzyme activities both capable of dephosphorylating all nucleoside 5-monophosphates with different efficiency and specificity. Broad-spectrum soluble 5'-nucleotidase is the object of this paper which deals with the definition of the response of this enzyme to effectors, some physiological and others not naturally occurring. The enzyme did not show any product regulation as all the nucleosides tested caused a moderate effect on the hydrolysis of the substrates. Theophylline and other xanthine derivatives had no effect on enzyme activity, whereas glycerate 2,3-bisphosphate, like other soluble 5'-nucleotidases, caused a stimulation of the enzyme, especially toward CMP and UMP. 5-Deoxy-5-isobutylthiadenosine resulted in no inhibition of the hydrolysis of AMP and IMP. The enzyme was affected neither by monovanadate nor by decavanadate, whereas it was strongly inhibited by Ap5 A. Variations in adenylate energy charge did not cause any alteration of the enzyme activity toward AMP and only a slight decrease of the hydrolysis of IMP. These regulatory properties, distinct from those of other soluble 5'-nucleotidases, show that this form, newly isolated from human seminal plasma, is subject to an almost unique, tissue-specific regulation.
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PMID:Human seminal plasma soluble 5'-nucleotidase: regulatory aspects of the dephosphorylation of nucleoside 5'-monophosphates. 923 3

Cytarabine (ara-C) requires activation into its triphosphorylated form, ara-CTP, to exert cytotoxic activity. Cytoplasmic 5'-nucleotidase (5NT) dephosphorylates ara-CMP, a key intermediate, preventing accumulation of ara-CTP and may reduce cellular sensitivity to the cytotoxic activity of ara-C. To determine whether the level of expression of 5NT is correlated with clinical outcome in patients with acute myeloid leukemia (AML) treated with ara-C, this study analyzed the levels of messenger RNA expression of high Km 5NT by real-time polymerase chain reaction at diagnosis in blast cells of 108 patients with AML. High Km 5NT was expressed at diagnosis in the blast cells of 54% of patients. In univariate analysis, (1) patients whose blast cells contained high levels (values greater than the median value for total population) of high Km 5NT at diagnosis had significantly shorter disease-free survival (DFS) than patients with low levels of high Km 5NT (11 months versus 17.5 months, P =.02) and (2) high levels of high Km 5NT also predicted significantly shorter overall survival (15.7 months versus 39 months, P = .01) in young patients (< or = 57 years; median value for the entire population). In a multivariate analysis taking into account age, karyotype risk, and other factors found to have prognostic significance in univariate analysis, (1) high Km 5NT expression was an independent prognostic factor for DFS and (2) high levels of high Km 5NT also predicted significantly shorter overall survival in young patients. These results demonstrate that the expression of high levels of high Km 5NT in blast cells is correlated with outcome in patients with AML.
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PMID:Expression of high Km 5'-nucleotidase in leukemic blasts is an independent prognostic factor in adults with acute myeloid leukemia. 1153 30

Erythrocyte maturation is accompanied by RNA degradation and release of mononucleotides. Pyrimidine 5'-nucleotidase, PN-I, has been purified and characterized. The molecular and enzymatic properties determined for the enzyme shows a 36-kDa and 5.1 pI monomeric protein with no disulfide bridges and no phosphate content. The activity is dependent on Mg(2+), while it is inactivated by heavy metals and by thiol-reactive reagents. PN-I is specific for pyrimidine nucleoside monophosphates, including the antineoplastic agents 5'-AZTMP and 5'-Ara-CMP. PN-I possess phosphotransferase activity able to exchange phosphate between pyrimidine nucleoside monophosphates and pyrimidine nucleosides, including AZT and Ara-Cyd. Amino acid sequence has been obtained from tryptic and CNBr peptides. PN-I cDNA sequence, coding for a 286-residue protein, has been retrieved from tag database, amplified by PCR, and expressed in Escherichia coli. The recombinant protein was fully active and showed identical properties with respect to PN-I. Substantial identity has been revealed with the partial sequences reported for p36, an alpha-interferon-induced protein. The significance of this identity is discussed.
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PMID:Human erythrocyte pyrimidine 5'-nucleotidase, PN-I. 1179 70


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