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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Extracellular nucleotides interact with specific receptors on the cell surface and are locally metabolized by ecto-nucleotidases. Biochemical characterization of the ATPase and ADPase activities detected in rat heart sarcolemma, under conditions where mitochondrial ATPase and adenylate kinase were blocked, supports our proposal that both activities correspond to a single enzyme, known as ATP-diphosphohydrolase or apyrase. The physiological function of this enzyme could be dephosphorylation of the nucleotides present in the interstitial heart compartment acting together with 5'-nucleotidase. Both hydrolytic activities have similarities in: sarcolemma localization, bivalent metal ion dependence, optimum pH, effect of several amino acid residue modifiers, competitive inhibition of nucleotide analogs, and broad nucleoside di-and triphosphate specificity. The ATPase activity could not be separated from the ADPase either through isoelectrofocusing or electrophoresis under acid conditions.
Biochem Mol Biol Int 1996 Aug
PMID:ATP-diphosphophydrolase activity in rat heart tissue. 886 7

The aim of the present study was to find out whether activities of the enzymes controlling adenosine metabolism, 5'-nucleotidase (5NT) and adenosine deaminase (ADA), in the left ventricle of the rat's heart change after 6 weeks of endurance or sprint training. Additionally, an influence of a single bout of endurance exercise till exhaustion on activities of these enzymes was investigated in sedentary and trained rats. The rats were divided into three groups: (1) sedentary controls (C), (2) endurance-trained (ET), and (3) sprint-trained (ST). It was shown that both types of training increased 5NT, but did not change ADA activity in the rat heart. Acute exercise till exhaustion did not affect 5NT activity in the heart taken from C and ST rats, but decreased its activity in the ET group. The heart ADA activity after exhaustive exercise increased in C and in ET group, but decreased in ST animals. It is concluded that physical training affects cardiac adenosine metabolism and the type of training may exert an influence on purine nucleotides metabolism in the heart during exhaustive exercise.
Biochem Mol Med 1996 Oct
PMID:Effect of various types of exercise training on 5'-nucleotidase and adenosine deaminase activities in rat heart: influence of a single bout of endurance exercise. 890 90

The human placental microvillar membrane contains several ectoenzymes, including 5'-nucleotidase, alkaline phosphatase and ATP-diphosphohydrolase (ATP-DPH), which might be involved in the extracellular metabolism of nucleotides. The type of anchorage to the plasma membrane of the two first enzymes has been shown to be via a glycosyl-phosphatidylinositol. In the present study, using an enzymatic approach, we show that the ATP-DPH should be attached to the plasma membrane through a different type of anchorage. We were also interested in the search of compounds which could interact differentially with this enzyme to be used as a tool for studying the other two hydrolytic enzymes in the presence of ATP-DPH. Here we report several inhibitors of ecto-ATPases which seem to be a useful tool for studying these three enzymes.
Res Commun Mol Pathol Pharmacol 1997 Apr
PMID:Human placental ecto-enzymes: studies on the plasma membrane anchorage and effect of inhibitors of ATP-metabolizing enzymes. 917 64

Periplasmic 5'-nucleotidase from Escherichia coli, in addition to the monophosphoesterase activity has a diphosphohydrolase activity, acting on nucleoside di- and triphosphates. We proposed that the monophosphoesterase and diphosphohydrolase activities have their own active site. This proposal is based on the different types of bonds being broken. Chemical modification with selective group reagents did not show differences in the essentiality of some residues, like histidyl, carboxyl and arginyl groups, of these two hydrolytic activities. While kinetic approaches employing the competition plot and unidirectional substrate inhibition point to that diphosphohydrolase activity (ATPase-ADPase) do not share the same active site with monophosphoesterase activity. Western blotting developed with polyclonal anti-placental apyrase antibody revealed a single protein in the periplasmic fraction of 66.5 kDa similar to the Mr of the purified enzyme by isoelectrofocusing.
Comp Biochem Physiol B Biochem Mol Biol 1997 May
PMID:Kinetic characteristics of nucleoside mono-, di- and triphosphatase activities of the periplasmic 5'-nucleotidase of Escherichia coli. 918 21

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.
Biochem Mol Med 1997 Jun
PMID:Human seminal plasma soluble 5'-nucleotidase: regulatory aspects of the dephosphorylation of nucleoside 5'-monophosphates. 923 3

Ectoenzymic activities capable of hydrolyzing ATP sequentially to adenosine are present on equine epidydimal spermatozoa membranes. Kinetic parameters for ATPase, ADPase and 5'-nucleotidase were obtained by analysis of progress reactions curve when ATP, ADP and AMP were supplied as initial substrates. These values are not different from those found when the substrates were supplied from the preceding reactions. Feed-forward inhibition on 5'-nucleotidase by ATP/ADP was taken into account to fit simulated data to the experimental results. None of the substrates supplied by the preceding reactions showed a preferential delivery to ADPase and/or 5'-nucleotidase. We therefore conclude that the model that fits the equine spermatozoa is that already proposed for pig aortic endothelial cells.
Comp Biochem Physiol B Biochem Mol Biol 1997 Aug
PMID:Hydrolysis of extracellular adenine nucleotides by equine epidydimal spermatozoa. 929 97

The effect of cyclic adenosine 3',5'-monophosphate (cAMP) on epileptiform activity in rat hippocampal slices was investigated. Bath-applied cAMP reversibly decreased the frequency of extracellularly recorded discharges in the CA3 subfield induced by bethanechol- or theophylline-containing solutions. Because cAMP was presumed to be relatively membrane impermeant, we developed and tested the hypothesis that this cAMP-mediated effect occurred extracellularly through the catabolic conversion of cAMP to 5'-AMP and, in turn, to adenosine, a known inhibitory neuromodulator. Three predictions derived from this catabolic hypothesis were tested. First, blockers of the enzymes involved were predicted to antagonize this effect of cAMP. In contrast, the coapplication of a cAMP-phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX), or a 5'-nucleotidase inhibitor, adenosine 5'-[alpha, beta-methylene] diphosphate (AMP-CP), enhanced the cAMP-induced suppressive effect. Second, the nonhydrolyzable cAMP analogs, dibutyryl- and 8-bromo-cAMP, were predicted to be ineffective. Low concentrations (5-40 microM) of these two derivatives, however, also suppressed bethanechol-induced discharges, while, at a higher concentration (100 microM), both analogs increased discharge frequencies. Third, enzymatic catabolism of adenosine was predicted to antagonize cAMP's effect, but coapplying adenosine deaminase (10 U/mL) did not diminish this action. Because these data did not support the catabolic hypothesis, other, as yet undefined, mechanisms must be responsible for the discharge-suppressant effect of cAMP.
Mol Chem Neuropathol 1997 Aug
PMID:Suppression of drug-induced epileptiform discharges by cyclic AMP in rat hippocampus. 933 68

Differences on 5'-nucleotidase activity in intact Rugli and BCS-TC2 cells (rat glioblastoma and human colon adenocarcinoma cell lines, respectively) are not due to differences in the characteristics of the ectoenzyme. A membrane-bound 5'-nucleotidase from BCS-TC2 cells has been purified to homogeneity with a high specific activity (130 U/mg), yielding a single 72-kDa band on SDS-PAGE. It is a metalloenzyme and, after inhibition by EDTA, its activity can be partially restored by divalent cations. The hydrolysis of the nucleosides 5'-monophosphate used as substrate follows Michaelis-Menten kinetics; ADP and concanavalin A are competitive and non-competitive inhibitors of the AMPase activity, respectively. This ecto-5'-nucleotidase is a high-mannose glycoprotein; deglycosylation converts the 72-kDa into a 59-kDa protein with a concomitant activity loss. The enzyme purified from BCS-TC2 cells shows similar characteristics from that previously isolated from Rugli cells; differences between them are mainly due to glycosylation. Polyclonal antibodies against 5'-nucleotidase from BCS-TC2 cells also show cross-reactivity with the enzyme from Rugli cells. When the ectoenzyme activity is measured in cells in culture, Rugli cells present a higher activity than BCS-TC2 cells however, they express very low amounts of ecto-5'-nucleotidase. Our results also show a reduction in protein level and enzyme activity associated with a decrease in the differentiation degree and an increase in tumorigenicity of human colon adenocarcinoma BCS-TC2 sublines.
Mol Cell Biochem 1998 Oct
PMID:Ecto-5'-nucleotidase from a human colon adenocarcinoma cell line. Correlation between enzyme activity and levels in intact cells. 978 49

AMP analogues modified at various positions of the molecule were checked as substrates for the two soluble isoforms of 5'-nucleotidase from human seminal plasma. These isoforms were isolated to near homogeneity by affinity chromatographies. AMP derivatives were differently dephosphorylated by both the isoforms depending on the site of modification in the natural compound. Changes in the phosphate moiety reduced significantly hydrolysis by the IMP-preferring form, whereas the AMP-preferring form was less affected. The AMP-preferring form was characterized by a relatively broad specificity toward substrate analogues indicating that the binding domains for the phosphate moiety of these isoforms are not identical. Substitutions at the C-8 adenine base reduced the hydrolysis rate of both the enzymes and variations of the syn-anti conformational equilibrium resulted in different effects on catalysis by both forms. Therefore, the orientation of the heterocyclic base around the glycosidic bond may not be the crucial factor affecting binding and catalytic activity. Hydrogen bonding potential of base N-7 was essential for the binding and catalysis of the IMP- but not of the AMP-preferring form. This was the most striking difference between the studied isoforms. Modifications and substitutions of 6-amino function, better accepted by the IMP-preferring form than by the AMP-preferring form, indicated that no essential hydrogen bonding is required for catalytic activity. The binding was however significantly slowed in 6-SH-PuMP. Hydrogen bonding potential of N-1 was significant for the hydrolysis rate of the IMP- but not of the AMP-preferring form. We suggest that these human seminal plasma isoforms of soluble 5'-nucleotidase, characterized by unique features, may represent the tissue-specific expression of the polymorphic gene.
Mol Genet Metab 1999 Jan
PMID:Activity of IMP- and AMP-preferring isoforms of 5'-nucleotidase from human seminal plasma with AMP analogues. 997 47

Although 5'-nucleotidases are ubiquitous in higher vertebrates, the arthropod enzymes have been little studied. The cDNA sequence of the mature 5'-nucleotidase from the tick Boophilus microplus was therefore determined (GENBANK accession number: U80634). The enzyme has 39-41% sequence identity with the vertebrate 5'-nucleotidases and contains binuclear metal ion binding sites. There are no significant introns within the coding region of the genomic sequence. Southern blot analysis indicates the presence of multiple related genes encoding 5'-nucleotidases. Recombinant tick 5'-nucleotidase was expressed in both Escherichia coli and in baculovirus-infected insect cells. The E. coli recombinant protein was truncated, inactive and produced in abundance. The enzyme was expressed in baculovirus-infected insect cells as a secreted, soluble, glycosylated and enzymatically active protein. This represents the first successful expression and characterization of enzymatically active recombinant 5'-nucleotidase from any organism. Supplementation of the culture medium with 25 microM zinc resulted in a twofold increase in the activity of the expressed protein. The enzyme was purified to homogeneity. It exists under non-denaturing conditions as a homodimer, with an apparent molecular mass of 135 kDa. The Km for the hydrolysis of AMP was 0.37 microM and the k(cat) = 11.5/s, in agreement with data for the native enzyme.
Insect Mol Biol 1999 May
PMID:Cloning and expression of ecto 5-nucleotidase from the cattle tick Boophilus microplus. 1038 Jan 9


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