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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
3 Pt 1
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pubmed:dateCreated |
1997-10-23
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pubmed:abstractText |
We investigated the extracellular degradation of diadenosine polyphosphates (ApnA) by cultured adrenomedullary endothelial cells using fluorogenic analogs of ApnA, the di(1,N6-ethenoadenosine) 5',5"'-P1,Pn-polyphosphates [epsilon-(ApnA)]. Kinetic parameters of epsilon-(ApnA) cleavage and effects of pH, ions, and inhibitors were determined by continuous fluorometric assays, using suspensions of endothelial cells grown on Cytodex-1 microspheres. Ecto-enzyme kinetic parameters for epsilon-(Ap3A), epsilon-(Ap4A), and epsilon-(Ap5A) hydrolysis are as follows: Michaelis-Menten constants of 0.39 +/- 0.07, 0.42 +/- 0.09, and 0.37 +/- 0.05 microM respectively, and maximal velocities of 26.1 +/- 6.8, 74.2 +/- 16.4, and 24.4 +/- 3.4 pmol.min-1.10(6) cells-1, respectively. ApnA and guanosine 5',5"'-P1,P4-tetraphosphate behave as competitor substrates of epsilon-(Ap4A) hydrolysis. The ectoenzyme is activated by Mg2+ and Mn2+ and inhibited by Ca2+, F-, adenosine 5'-tetraphosphate, adenosine 5'-O-(3-thiotriphosphate), and suramin. Optimum pH is around 9.0. High-performance liquid chromatography analysis reveals that the ecto-enzyme hydrolyzes epsilon-(ApnA) to give epsilon-adenosine-5'(n-1)-phosphate and epsilon-AMP, which are then further catabolized up to epsilon-adenosine via the membrane-bound nucleotidase system ecto-ATPase, ecto-ADPase (or apyrase), and ecto-5'-nucleotidase. The endothelial ecto-diadenosine polyphosphate hydrolase studied here exhibits different kinetic parameters and sensitivity to ions with respect to the enzyme from the tissue-related neurochromaffin cells. These different properties may be important in the extracellular signaling by ApnA.
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pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Cytodex,
http://linkedlifedata.com/resource/pubmed/chemical/Dextrans,
http://linkedlifedata.com/resource/pubmed/chemical/Dinucleoside Phosphates,
http://linkedlifedata.com/resource/pubmed/chemical/P(1),P(5)-di(adenosine-5'-)pentaphos...,
http://linkedlifedata.com/resource/pubmed/chemical/diadenosine tetraphosphate,
http://linkedlifedata.com/resource/pubmed/chemical/diadenosine triphosphate
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pubmed:status |
MEDLINE
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pubmed:month |
Sep
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pubmed:issn |
0002-9513
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:volume |
273
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
C918-27
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pubmed:dateRevised |
2006-11-15
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pubmed:meshHeading |
pubmed-meshheading:9316413-Adrenal Medulla,
pubmed-meshheading:9316413-Animals,
pubmed-meshheading:9316413-Cattle,
pubmed-meshheading:9316413-Cell Membrane,
pubmed-meshheading:9316413-Cells, Cultured,
pubmed-meshheading:9316413-Dextrans,
pubmed-meshheading:9316413-Dinucleoside Phosphates,
pubmed-meshheading:9316413-Endothelium, Vascular,
pubmed-meshheading:9316413-Exocytosis,
pubmed-meshheading:9316413-Hydrogen-Ion Concentration,
pubmed-meshheading:9316413-Hydrolysis,
pubmed-meshheading:9316413-Kinetics,
pubmed-meshheading:9316413-Microspheres,
pubmed-meshheading:9316413-Models, Biological
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pubmed:year |
1997
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pubmed:articleTitle |
Ecto-enzymatic hydrolysis of diadenosine polyphosphates by cultured adrenomedullary vascular endothelial cells.
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pubmed:affiliation |
Department of Biochemistry, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.
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pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
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