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)

Thymine-containing compounds, produced degradation of Escherichia coli DNA after infection of the cells with bacteriophage T5, did not accumulate in the cell but were excreted into the medium as the DNA was degraded. The ultimate degradation product was extracellular thymine that was not reutilized when T5 DNA synthesis began. This excretion of thymine may have been due in part to the induction of 5'-nucleotidase activity within 3 min after T5 infection. The level of this activity reached a maximum between 4 to 6 min after infection and then rapidly declined to its preinfection level by 10 to 15 min after infection. Chloramphenicol added before or soon after infection prevented the appearance of the nucleotidase. The induced nucleotidase activity was active not only on dTMP but also on dAMP, dGMP, and dCMP.
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PMID:Early events after infection of Escherichia coli by bacteriophage T5. Induction of a 5'-nucleotidase activity and excretion of free bases. 16 55

Deoxyadenosine metabolism was investigated in cultured human cells to elucidate the biochemical basis for the sensitivity of T lymphoblasts and the resistance of B lymphoblasts to deoxyadenosine toxicity. T lymphoblasts have a 20-to 45-fold greater capacity to synthesize deoxyadenosine nucleotides than B lymphoblasts at deoxyadenosine concentrations of 50--300 micron. During the synthesis of dATP, T lymphoblasts accumulate large quantities of dADP, whereas B lymphoblasts do not accumulate dADP. Enzymes affecting deoxyadenosine nucleotide synthesis were assayed in these cells. No substantial differences were evident in activities of deoxyadenosine kinase (ATP: deoxyadenosine 5'-phosphotransferase, EC 2.7.1.76) or deoxyadenylate kinase [ATP:(d)AMP phosphotransferase, EC 2.7.4.11]. The activity of 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) was increased 44-fold for AMP and 7-fold for dAMP in B lymphoblasts. A model for the regulation of deoxyadenosine nucleotide synthesis by 5'-nucleotidase activity is proposed on the basis of the observations.
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PMID:Biochemical basis for differential deoxyadenosine toxicity to T and B lymphoblasts: role for 5'-nucleotidase. 22 24

Residual 5'-nucleotidase activities in hemolysates from nine subjects with severe hereditary deficiency of pyrimidine nucleotidase (PyrNase) were compared to those in normal and reticulocyte-rich controls. Dephosphorylation rates of 12 potential ribo- and deoxyribomononucleotide substrates were measured as a function of pH. Data confirmed the existence of at least two isozymes of 5'-nucleotidase, PyrNase, and 2'-deoxy-5'-ribonucleotide phosphohydrolase (dNase) distinguishable by differences in maximal velocities, substrate preferences and restrictions, and pH optima. PyrNase was confirmed to be active principally with pyrimidine substrates (UMP = dCMP greater than CMP much greater than dTMP greater than dUMP) at a pH optimum of 7.5 +/- 0.1. dNase activity occurred with both purine and pyrimidine substrates and was maximal with deoxy analogs (dIMP much greater than dUMP greater than dGMP greater than dTMP = dAMP much greater than dCMP) at a pH optimum of 6.2, but slight cross-reactivity occurred with some nondeoxy substrates (IMP greater than GMP greater than UMP = XMP greater than CMP). PyrNase and dNase may be complementary systems that serve physiologically to clear the cytosol of RNA and DNA degradation products during maturation of erythroid elements by conversion of nucleotide monophosphates to diffusible nucleosides.
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PMID:Substrate specificity and pH sensitivity of deoxyribonucleotidase and pyrimidine nucleotidase activities in human hemolysates. 282 57

A purine 5'-nucleotidase has been separated by DEAE-Trisacryl chromatography from other 5'-nucleotidase activities present in human haemolysates and purified approx. 30,000-fold by subsequent chromatography on Blue Sepharose. The enzyme has an Mr of around 250,000, displays hyperbolic substrate-saturation kinetics and hydrolyses preferentially IMP, GMP and their deoxy counterparts. It is much less active with AMP and dAMP. The purine 5'-nucleotidase is inhibited by Pi, and is strongly stimulated by ATP, dATP and GTP, and by glycerate 2,3-bisphosphate. Stimulators decrease Km and increase Vmax. Glycerate 2,3-bisphosphate is the most potent stimulator of the enzyme and, under physiological conditions, over-rides the influence of the other effectors. Glycerate 2,3-bisphosphate also influences the binding of the enzyme to DEAE-Trisacryl, as evidenced by the different elution profile obtained with fresh as compared with outdated blood. It is concluded that the glycerate 2,3-bisphosphate-stimulated purine 5'-nucleotidase is responsible for the dephosphorylation of IMP and GMP, but not of AMP, in human erythrocytes.
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PMID:5'-Nucleotidase activities in human erythrocytes. Identification of a purine 5'-nucleotidase stimulated by ATP and glycerate 2,3-bisphosphate. 283 44

Several B lymphoblastic cell lines are known to be relatively resistant to the combination of 2'-deoxyadenosine with an adenosine deaminase inhibitor. These cell lines are believed to have a greater capacity to dephosphorylate 2'-deoxyadenosine nucleotides, thus preventing excessive accumulation of potentially toxic metabolites. In this study, the 2'-deoxynucleoside 5'-monophosphate dephosphorylating activities of human peripheral lymphocytes were examined. Peripheral lymphocytes have at least three nucleotide 5'-monophosphate nucleotidases distinguished by different pH optimums, substrate preference, Mg2+ requirement, inhibitors, and molecular weights. Two of the enzymes appeared to be cytosolic, only one of which had significant substrate activity with dAMP. This enzyme had an acidic pH optimum (5.0), no Mg2+ requirement, was inhibited by tartrate, and demonstrated broad substrate specificity. The other cytosolic nucleotidase required Mg2+, had a pH optimum of 5.5 to 6.0, was activated by 2'-deoxyinosine, and demonstrated a substrate preference for 3'- and 5'-monophosphate 2'-deoxynucleosides of hypoxanthine, guanine, uracil, and thymine. The third enzyme, ecto 5'-nucleotidase, is associated with the cell membrane. Although the ecto 5'-nucleotidase activity was higher in the B lymphocytes, the cytosolic nucleotidases were similar in activity in the T and B lymphocytes.
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PMID:Nucleotidase activities of human peripheral lymphocytes. 299 75

WI-L2 cells (a B-lymphoblastoid cell line) were more resistant than CEM cells (a T-lymphoblastoid cell line) to deoxyadenosine, ara-A (9-beta-D-arabinofuranosyladenine), or ara-C (1-beta-D-arabinofuranosylcytosine) inhibition. This was caused by a difference in the composition of cytosol 5'-nucleotidases between WI-L2 and CEM cells. In intact cells, the endogenous production of deoxyadenosine from WI-L2 cells deficient in adenosine kinase (EC 2.7.1.20) and deoxycytidine kinase (EC 2.7.1.74) was consistently high, despite changes in endogenous adenosine production. Endogenous production of deoxyadenosine from CEM cells deficient in adenosine kinase and deoxycytidine kinase was, however, coordinated with endogenous adenosine production. In broken cells, cytosol dAMPase (2'-deoxyadenosine 5'-monophosphate 5'-nucleotidase) activity of WI-L2 cells was 3-5-fold higher than that of CEM cells. dAMPase activity could be separated from ATP-activated IMPase (inosine 5'-monophosphate 5'-nucleotidase) by gel filtration (molecular weight: dAMPase; 39,000-46,000; ATP-activated IMPase, greater than 150,000). Cytosol ATP-activated IMPase and dAMPase were isolated by phosphocellulose or DEAE-Bio-Gel A chromatography from non-specific phosphatases. The ATP-activated IMPase showed only marginal activity towards dAMP (2'-deoxyadenosine 5'-monophosphate), ara-AMP (9-beta-D-arabinofuranosyladenine 5'-monophosphate), or ara-CMP (cytosine-beta-D-arabinofuranoside 5'-monophosphate), even in the presence of ATP. The activity of ATP-activated IMPase was similar in WI-L2 and CEM cells. dAMPase was separated into two peaks by DEAE-Bio-Gel A chromatography; one of these peaks degraded ara-AMP and ara-CMP. The activities of both peaks from WI-L2 cells were higher than those from CEM cells. These results show that the degradation of dAMP, ara-AMP or ara-CMP was more specific and rapid in WI-L2 than in CEM cells.
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PMID:Differential composition of cytosol 5'-nucleotidases between T and B lymphoblasts. 301 Nov 14

The contribution of plasma membrane 5'-nucleotidase (E.C. 3.1.3.5) to intracellular purine degradation and release was evaluated in cultured human lymphoblasts. B-lymphoblasts and T-lymphoblasts are characterized by high and low levels of plasma membrane 5'-nucleotidase activity, respectively. After radiolabeling of the cellular adenine nucleotide pools with [8-14C]adenine, deoxyglucose-induced purine nucleotide degradation resulted in a 2-2.5 times greater release of cellular radioactivity from the B-lymphoblasts than from the T-lymphoblasts. Specific inhibition of plasma membrane 5'-nucleotidase with 50 microM alpha, beta-methylene adenosine diphosphate (AMPCP) did not decrease purine release during deoxyglucose-induced nucleotide degradation. Similarly, the inhibition of B-lymphoblast membrane 5-nucleotidase did not alter the incorporation of [8-14C]adenine into the nucleotide pool. Therefore, to explain the relatively high release of purine nucleotide degradation products in B-lymphoblasts when compared with T-lymphoblasts, cytoplasmic 5'-nucleotidase activity was investigated in these cell lines. B-lymphoblasts have seven times more cytoplasmic 5'-nucleotidase activity for dAMP and two to three times more activity for other purine nucleoside 5'-monophosphates than do T-lymphoblasts at pH 7.4. Membrane and cytoplasmic nucleotidase activities are produced by different enzymes that can be distinguished by differences in pH optima, Michaelis constants for purine substrates, divalent cation requirements, and susceptibilities to AMPCP inhibition. The data suggest that plasma membrane 5'-nucleotidase hydrolyzes extracellular nucleoside 5'-monophosphates only. Cytoplasmic 5'-nucleotidase most likely regulates the degradation of intracellular nucleoside 5'-monophosphates and may be responsible for the increased purine release observed in B-lymphoblasts.
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PMID:Regulation of purine metabolism by plasma membrane and cytoplasmic 5'-nucleotidases. 629 1

The persistence of normal thymidine nucleotidase (ThyNase) activity in subjects with pyrimidine nucleotidase (PyrNase) deficiency suggested the possible existence of separate isozymes in normal human erythrocytes. This hypothesis was confirmed by studies of PyrNase-deficient individuals from five unrelated families. Erythrocytes deficient in PyrNase retained normal activity of an enzyme system preferentially active at pH 6.2 with a variety of 2'-deoxyribonucleoside 5'-monophosphate substrates, including those of uridine, thymidine, and cytidine. Lesser activities were observed with the corresponding ribonucleotides. Normal control hemolysates were also found capable of effectively dephosphorylating purine nucleotides (dAMP greater than AMP) when pH was lowered sufficiently from the pH 7.4-8.0 region commonly used in conventional assays. Variations in substrate specificity, pH optima, kinetics, and sensitivity to inactivation by Pb2+ indicated the existence of multiple 5'-nucleotidase isozymes in normal erythrocytes: PyrNase and deoxyribonucleotidase(s) that might function physiologically in the conversion of DNA-derived nucleotides to diffusible nucleosides. Evolution of such a unique 5'-nucleotidase suggests that normal erythroblast maturation and nuclear extrusion is accompanied by a degree of karyolysis sufficient to require dephosphorylation and clearance of DNA degradation products.
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PMID:Identification of thymidine nucleotidase and deoxyribonucleotidase activities among normal isozymes of 5'-nucleotidase in human erythrocytes. 632 Jan 96

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

5'-Nucleotidase specific towards dCMP and AMP was isolated from avian breast muscle and characterized. It was found to be similar to a type-I form (cN-I) identified earlier as the AMP-selective 5'-nucleotidase responsible for adenosine formation during ATP breakdown in transfected COS-7 cells. Expression pattern of the cN-I gene in pigeon tissues indicated breast muscle as a rich source of the transcript. We purified the enzyme from this source using two-step chromatography and obtained an active homogenous preparation, free of ecto-5'-nucleotidase activity. The tissue content of the activity was calculated at 0.09 U/g wet weight. The specific activity of the enzyme preparation was 4.33 U/mg protein and it preferred dCMP and AMP to dAMP and IMP as a substrate. Its kinetic properties were very similar to those of the enzyme purified earlier from heart tissue. It was strongly activated by ADP. Inhibition by inorganic phosphate was more pronounced than in heart-isolated cN-I. Despite this difference, a similar physiological function is suggested for cN-I in both types of muscle.
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PMID:Isolation and characterization of pigeon breast muscle cytosolic 5'-nucleotidase-I (cN-I). 1594 Mar 49


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