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

An enzyme capable to split adenosine triphosphate (ATP) was shown to be firmly associated with mature herpes simplex virus particles purified from infected rabbit lung (ZP) cells. The enzyme localized in the viral envelope was markedly activated by bivalent cations, to the largest degree by Mg2+ at a pH optimum of 7.8--8.0. Na+ and K+ ions neither separately nor together showed any activating effect. Enzyme activity was not sensitive to the action of ouabain. No adenosine diphosphatase (ADPase) and adenosine monophosphatase (AMPase) activities were observed. ATPase activity was competitively inhibited by ADP. AMP and inorganic phosphate were without effect. The ATPase of nuclear membranes isolated from ZP cells exhibited similar properties but behaved differently to the action of sodium dithionite, dinitrophenol, oligomycin and gramicidin, as well as on heat inactivation. The origin of the virus enzyme is discussed.
 ...
PMID:Some properties of the adenosine triphosphatase associated with herpes simplex virus and nuclear membrane of host cells. 2 4

5'-Nucleotidase, assayed as 5'-AMPase, has been extensively characterized and established as a stable, quantitative plasma membrane marker in HeLa S3 cells. The membrane 5'-AMPase has a Km of 7.0 microM. Relative affinities of the other 5'-mononucleotides for the enzyme are 5'-GMP > 5'-TMP > 5'-UMP > 5'-CMP. There are activity optima at pH7 and 10; the latter is Mg(2+)-dependent. The membrane preparations have a small amount of acid phosphatase activity that is distinct from 5'-AMPase activity but no alkaline phosphatase. AOPCP, ADP, and ATP are strongly inhibitory. Mg2+, Ca2+, or Co2+ additions do not affect the pH 7.0 activity; Mn2+ activates slightly, whereas Zn2+, Cu2+, and Ni2+ are inhibitory. EDTA slowly inactivates, but removal of the EDTA without the addition of divalent cations restores activity. The inactivation is also substantially reversed by Co2+ or Mn2+, but reactivability by divalent cations decreases with time in EDTA. ConA strongly inhibits, and alpha-methyl-D-mannoside or glucose (the latter much less efficiently) relieves the inhibition, indicating that the 5'-AMPase is a glycoprotein. Histidine is also inhibitory. Ouabain, phloretin, cytochalasin B, cysteine, phenyl-alanine, MalNEt, and IAA are without effect. 5'-AMPase activity codistributes with pulse-bound [3H]ouabain when either of two cell fractionation procedures are used. The 5'-AMPase activity per cell is constant at different cell densities in exponentially growing cells, and activity per unit cell volume remains constant throughout the cell cycle. These properties, together with its absence in other organelles, its stability to storage, its insensitivity to certain experimental manipulations, and its general insensitivity to inhibitors of specific transport systems, make 5'-AMPase a useful quantitative marker in studies on the regulation of HeLa membrane transport systems. Key Words: HeLa, 5'-nucleotidase, plasma membrane marker, non-specific phosphatases, divalent ions, ConA, AOPCP, cell cycle, mitochondria, transport inhibitors.
 ...
PMID:Characterization of HeLa 5'-nucleotidase: a stable plasma membrane marker. 4 80

In the present paper the mechanism of the adenosine formation by a mixture of nerve ending and transmitter granula fractions was invesitgated. The adenosine formation in vivo is only possible via the whole degradation chain ATP - ADP - AMP - adenosine. The enzymes involved are ATPases, adenylate kinase and 5'-nucleotidase. The ATPase and adenylate kinase effectors Ca++ and Mg++ can be regarded as trigger ions switching on and off the degradation chain. The adenylate kinase represents a key enzyme within the whole chain. In the ion-activated state a non-inhibited adenosine formation was observed, when the initial ATP concentration amounted to less than 0,1 muMol per mg synaptosomal membrane protein. Under these conditions the whole chain velocity is mainly dependent on the 5'-nucleotidase concentration, because ATPases and adenylate kinase remove the nucleotidase inhibitors ATP and ADP spontanously. The conditions for the optimal velocity of the adenosine formation at the synaptic membrane in vivo in all probability are present. A hypothesis for the mechanism of the synaptic adenosine formation in vivo was developed. The importance of this process in respect to the synaptic transmission was discussed.
 ...
PMID:[Mechanism of synaptosomal degradation of ATP in connection with involvement of adenosine in the transmission process]. 12 26

The properties of a Ca2+ activated adenosine triphosphatase shown to be present in homogenates of purified rat peritoneal mast cells were investigated. The enzyme was activated by Ca2+, Mg2+, and to a lesser extent by Mn2+ and Co2+. Ca2+ alone was necessary for full activity and the further addition of Mg2+ did not have any effect. The chelating agents EGTA (ethanedioxybis(ethylamine)tetra-acetate) and EDTA completely inhibited the reaction. The pH optimum was 7.8. Reduced glutathione, cysteine, dithiothreitol, N-ethylmaleimide, urea, ADP, NaF, increasing ionic strength and Triton X-100 all inhibited the reaction. On subcellular fractionation of mast-cell homogenates by density-gradient centrifugation, the distribution of Ca2+ activated adenosine triphosphatase resembled that of 5'-nucleotidase, but differed from that of the other markers used, suggesting localization in the plasma membrane. Further experiments indicated that the enzyme is present on the external surface of the plasma membrane.
 ...
PMID:Characterization of calcium-ion-activated adenosine triphosphatase in the plasma membrane of rat mast cells. 13 82

The purpose of this study was to try to differentiate histochemically between the various enzymes which may catalyze the hydrolysis of ATP in developing rat dental tissues. Freeze cut and freeze dried sections of molar and incisor teeth were incubated in lead capture-based media at pH 5.0, 7.2 or 9.4 with one of the following substrates: beta-glycerophosphate, AMP, ADP, ATP, AMP-PNP and tetrasodium pyrophosphate. To establish the enzymatic nature of the hydrolysis parallel sections were incubated after prior fixation in either formaldehyde or glutaraldehyde. By comparing the enzymatic stainings obtained with the various substrates and at the different pH:s, it was concluded that ATP can be visibly hydrolyzed in rat dental tissues by alkaline phosphatase (stratum intermedium, apical part of maturation ameloblasts, basal part of all ameloblasts, odontoblasts and subodontoblastic layer), specific ATPase (apical and basal parts of secretory ameloblasts) and ATP pyrophosphatase and/or adenylate cyclase (stratum intermedium, odontoblasts). Acid phosphatase, specific ADPase, 5'-nucleotidase, inorganic pyrophosphatase, 3':5'-cyclic-AMP-phosphodiesterase and adenylate kinase on the other hand, seem not to be engaged in the ATP hydrolysis to such a degree as to complicate the interpretation of the histochemical staining. The alkaline phosphatase part of the ATP hydrolysis appeared to be rather insensitive to aldehyde fixation, while the hydrolysis effected by specific ATPase and ATP pyrophosphatase and/or adenylate cyclase was extinguished after fixation with formaldehyde for 4 h or glutaraldehyde for 10 min.
 ...
PMID:Adenosine triphosphate hydrolysis in rat dental tissues. A histochemical study to differentiate the enzymes involved. 18 60

1. Isolated nerve terminals (T-sacs and synaptosomes) prepared from the purely cholinergic Torpedo electric organ have been studied for their ability to incorporate and metabolise [2-3H] adenosine and to degrade 5'-AMP to adenosine. 2. A temperature-dependent, saturable uptake system for adenosine was found with kinetic properties similar to nucleoside transport systems in other cells. The uptake system in Torpedo nerve terminals was inhibited by 2'-deoxyadenosine, a known inhibitor of adenosine transport. 3. Intraterminal adenosine is rapidly metabolised to a number of products including AMP, ADP and ATP. 4. Isolated nerve terminals contain considerable 5'-nucleotidase activity, most of which resides on the outer face of the external membrane. The Km of the enzyme is congruent to 5 micron and it is inhibited by a phosphonate analogue of ADP, alpha-beta-methylene-ADP. It is suggested that this 5'-nucleotidase plays an important role in the production of adenosine from a nucleotide pool in the synaptic cleft.
 ...
PMID:Adenine nucleotides in cholinergic transmission: presynaptic aspects. 21 98

Radioactively labelled adenosine and adenine were rapidly taken up by isolated rat fat cells, and incorporated into nucleotides, of which ATP dominated. The overall process had an apparent Km of 1--5 micrometers. During incubation, especially in the presence of lipolytic agents, there was a reduction in labelled ATP with a compensatory increase in ADP, AMP, cAMP and nucleosides. The build-up of adenosine during incubation was inhibited by theophylline, which inhibits 5'-nucleotidase. Radioactivity released from perifused fat cells consisted mainly of nucleoside material, of which adenosine predominated. Lipolytic stimulation caused no significant increase in nucleoside outflow from perifused cells, whereas oxygenation was capable of reducing this outflow. It is concluded that adenosine is formed by fat cells as a consequence of ATP breakdown. Stimulation of lipolysis during activation of the sympathetic nerves leads to reversible ATP breakdown and adenosine release. Adenosine might therefore act as a modulator of lipolysis in vivo under these conditions, even though it does not serve as a feed back regulator in the proper sense.
 ...
PMID:Uptake and release of adenosine in isolated rat fat cells. 22 Aug 45

A procedure is presented for the rapid purification of a 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) from potato tubers, involving ammonium sulphate fractionation and chromatography on phosphocellulose, DEAE-cellulose and Sephadex G-75. Application of this procedure results in a 6000-fold purification of the 5'-nucleotidase and the final preparations are virtually homogeneous, yielding only one protein band on electrophorsis in polyacrylamide gels in non-dissociating or dissociating conditions. The 5'-nucleotidase has a molecular weight of 50 000 from gel filtration experiments. Sodium dodecylsulphate-polyacrylamide gel electrophoresis of the purified 5'-nucleotidase reveals one major band of molecular weight 25 000. The 5'-nucleotidase is competitively inhibited by cyclic nucleotides, having micromolar Ki values for cyclic AMP and cyclic GMP at pH 5.0 and pH 8.0. The enzyme has a pH optimum of 5.0 with 5'-GMP as substrate. While 5'-AMP and 3'-AMP are hydrolyzed at comparable rates at pH 5.0, at pH 8.0 the rate of hydrolysis of 3'-AMP is only 4% of that with 5'-AMP. ADP, ATP and 2'-AMP are very poor substrates for the enzyme. The nucleotidase has micromolar Km values for nucleoside 5'-monophosphates other than 5'-NMP. A wide variety of divalent cations activate the 5'-nucleotidase.
 ...
PMID:Purification and characterization of a cyclic nucleotide-regulated 5'-nucleotidase from potatoe. 23 99

Adenine nucleotide breakdown to nucleosides and purine bases was measured in cultures of human lymphoblastoid cells following: 1) the inhibition of oxidative phosphorylation in the absence of glucose or 2) the addition of 2-deoxyglucose. A mutant cell line, deficient in adenosine kinase, in the presence of an adenosine deaminase inhibitor was used to measure utilization of the two pathways of AMP catabolism involving initial action of either purine 5'-nucleotidase or AMP deaminase. In such a system the appearance of adenosine induced by the oxidative phosphorylation inhibitor, rotenone, implies that approximately 70% of AMP breakdown occurs via dephosphorylation. By the same method, deamination accounts for 82% of AMP breakdown when 2-deoxyglucose is added. The occurrence of AMP dephosphorylation is not correlated with elevated concentrations of substrate or with decreased concentrations of the inhibitors of 5'-nucleotidase, ATP and ADP. Dephosphorylation occurs if, and only if, the adenylate energy charge decreases to about 0.6 in these experiments. In cultures deprived of glucose and oxygen, adenine nucleotide degradation via dephosphorylation results in recovery of normal energy charge values.
 ...
PMID:Adenine nucleotide degradation during energy depletion in human lymphoblasts. Adenosine accumulation and adenylate energy charge correlation. 47 72

Rat hearts were perfused simultaneously with [8-3H] AMP and [8-14C]adenosine. [8-3H] AMP was hydrolzyed by 5'-nucleotidase to produce intra- and extracellular [8-3H] adenosine. Comparison of the specific activities of [3H]- and [14C]adenosine in the heart cells with the specific activities of [3H]- and [14C]adenosine in the effluent perfusate showed that much more [3H]adenosine accumulated in the tissue than would be expected if extracellular adenosine were the immediate precursor of intracellular adenosine. Conversely, perfusion of rat hearts with [8-14C]AMP and [8-3H]adenosine led to a much greater accumulation of intracellular [14C]adenosine than would be expected from an uptake of adenosine from the perfusate. These results are interpreted to be due to hydrolysis of extracellular AMP by 5'-nucleotidase, located in the plasma membrane, and release of the resulting adenosine inside the cell. Measurements of the specific activities of 3H and 14C in ATP, ADP, AMP, and inosine support this interpretation.
 ...
PMID:Vectorial production of adenosine by 5'-nucleotidase in the perfused rat heart. 62 28


1 2 3 4 5 6 7 8 9 10 Next >>