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)

In this study we report that preincubation of Dictyostelium discoideum membrane-bound adenylate cyclase with ATP over the concentration range 0.5 to 100 mM results in a loss of catalytic activity and that this effect persists even after removal of ATP. An analysis of the time course of this effect shows that, at 25 mM ATP, a 5- to 10-min preincubation results in 50% loss of activity. Additional studies on this effect showed that anhydride bond cleavage of ATP occurs during the preincubation. However, loss of catalytic activity is not porduced by ADP, AMP, cAMP, adenosine, pyrophosphate, or phosphate either separately or in pairs. Further, using the structural analogs adenosine 5'-(alpha, beta-methylene)triphosphate and adenyl-5'-yl imidodiphosphonate, we show that there is a direct correlation between alpha-beta-phosphoanhydride bond cleavage and the loss of catalytic activity. These results can be interpreted in terms of two classes of reaction mechanisms: either those involving covalent modifications or those involving a ligand-induced slow conversion of the adenylate cyclase from an active to an inactive form. Additional studies show that the addition of AMP to the reaction mixture, as well as removal of the membrane-bound 5'-nucleotidase activity, can prevent the loss of cyclase activity. These results suggest not only that adenylate cyclase activity is related to the AMP:ATP ratio but that the cyclase activity can be modified by the level of 5'-nucleotidase activity. Studies on the duration of the loss of activity produced by ATP show that following removal of ATP and additional incubation, a gradual recovery of cyclase activity is observed. This result suggests that under appropriate conditions the cyclase inactivation by ATP is reversible.
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PMID:Time-dependent changes in Dictyostelium discoideum adenylate cyclase activity upon incubation with ATP. 98 25

The 5'-phosphomonoesterase activity of 5'-nucleotidase (EC 3.1.3.5) and alkaline phosphatase (EC 3.1.3.5) participates in the catabolism of purine ribonucleotides to uric acid in humans. Initial velocity studies of 5'-nucleotidase suggest a sequential mechanism of interaction between AMP nad MgCl2, with a Km of 14 and 3 muM, respectively. With product inhibition studies the apparent Ki's for adenosine, inosine, cytidine, and inorganic phosphate were 0.4, 3.0, 5.0, and 42 mM, respectively. A large number of nucleoside mono-, di-, and tri-phosphate compounds were inhibitors of the enzyme. Allopurinol ribonucleotide, ADP, or ATP were competitive inhititors when AMP was the substrate, with a Ki slope of 120 muM. The phosphomonoesterase activity of human placental microsomal alkaline phosphatase had a pH optimum of 10.0 and had only 18% of maximum activity at pH 7.4. Substrates and inhibitors included almost any phosphorylated compound. The Km for AMP was 0.4 mM and the apparent Ki for Pi was 0.6 mM. Activity was increased only 19% by 5 mM MgCl2. These observations suggest that 5'-nucleotidase and alkaline phosphatase may be inhibited by ATP and Pi, respectively, under normal intracellular conditions, and that AMP may be preferentially hydrolyzed by 5'-nucleotidase.
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PMID:Purine catabolism in man: inhibition of 5'-phosphomonesterase activities from placental microsomes. 101 16

Adenine nucleotides and adenosine are known to be of importance in the regulation of coronary function. This made a study of the effect of neurohormone "C" on the metabolism of adenine nucleotides and adenosine interesting in as much as neurohormone "C" dilates coronary vessels and has a direct metabolic effect on cardiac muscle. The results obtained have shown that incubation of cardiac muscle homogenates with labelled ATP increased the content of adenosine through raising 5'-AMP nucleotidase activity and inhibiting adenosine deaminase activity. In homogenates and slices of brain tissue the content of adenosine is, on the contrary, reduced. Opposite changes are observed in the content of AMP. The increase of adenosine in the heart by the increase of 5'-AMP nucleotidase activity and decrease of adenosine deaminase activity is probably, not the main factor of the coronarodilatatory effect of neurohormone "C". The reverse phenomena is noticed in brain, the functional significance of which must be studied. However, the role of adenosine in the mechanism of action of neurohormone "C" will become clear after in vivo experiments which are in progress.
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PMID:[Effect of neurohormone "C" on adenine nucleotide and adenosine metabolism in rat heart and brain]. 103 20

The subcellular localization of adenylate cyclase (ATP pyrophosphatelyase (cyclizing), EC 4.6.1.1) in bovine corpus luteum was studied using isotonic and hypotonic homogenization and fractionation conditions. All fractions prepared were assayed for adenylate cyclase, marker enzymes and DNA. Only plasma membrane marker enzyme, 5'-nucleotidase paralleled the distribution of adenylate cyclase under both isotonic and hypotonic conditions (conditionsoth isotonic and hypotonic conditions (coefficient of correlation = 0.95). Two main fractions prepared under hypotonic conditions were subfractionated by discontinuous sucrose gradient centrifugation. The highest amount of adenylate cyclase was found in a fraction having a density approximately equal to 1.13 g/cm3. The specific activity of this fraction was 4--6 times higher than that of the homogenate. The electron microscopic study of this fraction revealed the presence of a single type of particulate material consisting of small vesicles exhibiting a typical unit membrane structure. It is concluded that this adenylate cyclase is primarily localized in the plasma membranes. Basal adenylate cyclase activity of plasma membranes was stimulated 2--3 times by luteinizing hormone (10 mug/ml), 3--4 times by prostaglandin E2 (10 mug/ml), 4--6 times by NaF (0.01 M) and two times by methanol (0.2%).
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PMID:Subcellular localization and partial characterization of bovine corpus luteum adenylate cyclase. 114 60

5'-Nucleotidase prepared from muscle of small intesting of pig is strongly inhibited by nucleoside di- and triphosphates and their phosphonate analogs. Substrate kinetics appromate the Michaelis-Menten for for AMP, which shows a Km of 3-6 muM at pH 5.3-7.2. Inhibition is characterized as partial competitive, except at pH 5.3, where inhibition by ATP is noncompetitive. The Ki values for several inhibitors have been determined, and their departure from completeness of competitive inhibition has been studied. Inhibitor cooperativity of the type reported for the enzyme from sheep brain (P. L. Ipata (1968), Biochemistry 7, 507) was not observed for the enzyme from gut. In addition we failed to confirm sigmoid inhibition kinetics with 5'-nucleotidase from sheep brain.
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PMID:5'-Nucleotidase from smooth muscle of small intestine and from brain. Inhibition of nucleotides. 116 62

5'-Nucleotidase in perfused rat hearts, accessible to extracellular substrate [14C]-AMP contained in the perfusate, was compared to a partially purified 5'-nucleotidase from the same organ. Both activities were inhibited by ATP and, more effectively, by the ADP analog adenosine-alpha, beta-methylene diphosphate (APCP). The isolated enzyme showed a competitive inhibitor constant of 5.4 x 10(-8) M for APCP (Km of AMP = 1.4 x 10(-5) M). Although both activities were effectively inhibited by APCP, insufficient knowledge about the selectivity of this agent as a nucleotidase inhibitor does not permit a conclusion on whether or not the extracellular activity is identical to the partially purified enzyme.
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PMID:Inhibition of extracellular and purified 5'-nucleotidase from rat heart. 120 4

The present state of investigations on molecular and cellular mechanisms of cardioprotective effects of phosphocreatine (PCr) is reviewed. The protective effect of PCr is manifested as significant improvement of heart contractile function recovery, lowering of diastolic pressure elevation and myocardial enzymes release during postischemic reperfusion as well as better preservation of high energy phosphates in comparison with control. Data from multidisciplinary studies using physico-chemical, physiological, pharmacological etc. approaches suggest that one of the key mechanisms of PCr action is its interaction with the sarcolemmal membrane. The authors own data obtained with the use of spin-labeled ESR-probe incorporated into the isolated sarcolemmal vesicles provide direct evidence in favor of the ordering effect of PCr sarcolemmal phospholipid packing with essential involvement of Ca2+ ions. PCr transform membrane phospholipids into more structured gel-like state. The results of biomedical studies suggest that the mechanism of this protective action is complex and includes at least four components: 1) inhibition of lysophosphoglyceride accumulation in the ischemic myocardium and preservation of cardiac cell sarcolemma structure via zwitterionic interaction with PCr molecules; ii) extracellular action consisting in inhibition of platelet aggregation via ADP removal in the extracellular creatine kinase reaction and increasing plasticity of red blood cells; iii) PCr penetration into cells maintenance of high local ATP levels is possible; iiii) inhibition of adenine nucleotide degradation at the step of 5'-nucleotidase reaction in cardiac cell sarcolemma.
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PMID:[Molecular and cellular aspects of the cardioprotective mechanism of phosphocreatine]. 129 51

The regulation by ATP of Cl- secretion in T84 cells grown on filters was investigated by measuring short-circuit current (Isc = net Cl- secretion). ATP (greater than or equal to 10 microM) added to the basolateral side markedly stimulated Isc both in the presence and absence of forskolin-activated Isc. Fluorescence microscopy of cells loaded with the Ca2+ indicator fura-2 showed that ATP stimulated a transient increase in intracellular free Ca2+ concentration [Ca2+]i. The augmentation of forskolin-stimulated Isc by ATP was at least partly caused by mobilization of Ca2+ from an internal store because prior depletion of the store using ionomycin prevented the response. The activity sequence for stimulation of Isc in the presence of forskolin was adenosine 5'-O-(3-thiotriphosphate) = 5'-adenylylimidodiphosphate (AMP-PNP) greater than ATP greater than ADP greater than AMP, suggesting the presence of a P2 purinergic receptor. Neither beta, gamma-methyleneadenosine 5'-triphosphate nor alpha, beta-methyleneadenosine 5'-triphosphate increased the Isc. Stimulation of Isc by ATP in the absence of forskolin was at least partly due to the breakdown of ATP to AMP and adenosine, which act at P1 receptors to stimulate Isc, since 1) inhibition of the ecto-phosphohydrolase 5'-nucleotidase by alpha, beta-methylene-ADP partially inhibited stimulation of Isc by ATP, 2) the adenosine receptor antagonists caffeine and 8-phenyltheophylline markedly inhibited the ATP-stimulated Isc, and 3) AMP-PNP, a weakly hydrolyzable analogue of ATP, caused a much smaller increase in Isc compared with ATP. Adenosine had no effect on [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Purinergic receptor activation of Cl- secretion in T84 cells. 131 Feb 17

Renal epithelial function, proton flux and sodium stimulated proton flux, was observed in vesicles isolated from the brush border of the proximal tubule of Sockeye Salmon (Oncorhynchus nerka) during migration. Brush border membrane vesicles (BBMV) were isolated from the body kidney of Sockeye Salmon using aggregation/differential centrifugation techniques. Vesicle purity was tested using a series of epithelial and basal lateral markers including alkaline phosphatase, maltase, gamma-glutamyl transferase (GGTP), Mg(2+)-activated ATP-ase, Na(+)+K(+)-activated ATPase, and 5'-nucleotidase and the lysosomal marker acid phosphatase. An enrichment/depletion factor for each marker was determined by comparison of purified BBMV with kidney homogenate. Vesicles exhibit an enrichment factor for alkaline phosphatase, GGTP, maltase, Mg(2+)-activated ATP-ase, Na(+)+K(+)-activated ATPase, and 5'-nucleotidase. A depletion factor was observed for acid phosphatase. Vesicle integrity was tested by measuring the time course of proton flux in the presence of a pH gradient. Amiloride sensitive sodium stimulated proton flux was observed in these vesicles. The presence of sodium caused a saturable increase in the rate of proton flux, indicating the activity of a sodium/proton antiport protein in BBMV.
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PMID:Proton transport and Na+/H+ exchange in vesicles isolated from sockeye salmon (Oncorhynchus nerka) kidneys during migration from salt to fresh water. 132 4

We have investigated the kinetic properties of the extracellular reaction sequence ATP----ADP----AMP----adenosine catalyzed by ectonucleotidases at the surface of adult rat cardiac myocytes. Analysis of progress of reaction curves indicates that depletion of substrate at cell surfaces dominates the regulation of the rate of hydrolysis of ATP or of ADP when it is the initial substrate. Preferential delivery of intermediate products to be substrates at cell surfaces makes a significant contribution to the regulation of adenosine production from ATP or ADP. Preferential delivery has more impact on the delivery of ADP from adenosinetriphosphatase (ATPase) to adenosinediphosphatase (ADPase) than on delivery of AMP from ADPase to 5'-nucleotidase. At high initial ATP concentrations, feed-forward inhibition of AMP hydrolysis also modulates the rate of adenosine production. Taken together, the properties of the ectonucleotidases on the myocyte provide a milieu at the cell surface that tends to be poor in nucleotides, especially ATP and ADP (P2 purinoceptor agonists), and rich in adenosine (a P1 purinoceptor agonist) during periods of supply of extracellular nucleotides.
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PMID:Regulation of extracellular adenosine production by ectonucleotidases of adult rat ventricular myocytes. 132 61


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