An Ecto-Nucleotide Pyrophosphatase Is One of the Main Enzymes Involved in the Extracellular Metabolism of ATP in Rat C6 Glioma
| Autor: | Herman Slegers, Bert Grobben, Eddy L. Esmans, Katelijne Anciaux, Mathieu Bollen, Cristiana Stefan, Dirk Roymans |
|---|---|
| Rok vydání: | 1999 |
| Předmět: |
Adenylate kinase
Biology Biochemistry Cellular and Molecular Neuroscience chemistry.chemical_compound Adenosine Triphosphate ATP hydrolysis Tumor Cells Cultured Animals PPADS Enzyme Inhibitors Phosphorylation Pyrophosphatases Pyrophosphatase Hydrolysis Stem Cells Autophosphorylation Receptors Purinergic Glioma Molecular biology Nucleoside-diphosphate kinase Rats chemistry Astrocytes Nucleoside-Diphosphate Kinase Pyridoxal Phosphate Guanosine Triphosphate Extracellular Space Phosphorus Radioisotopes Nucleoside Adenosine triphosphate Platelet Aggregation Inhibitors |
| Zdroj: | Journal of neurochemistry |
| ISSN: | 0022-3042 |
| DOI: | 10.1046/j.1471-4159.1999.0720826.x |
| Popis: | The presence of a nucleotide pyrophosphatase (EC 3.6.1.9) on the plasma membrane of rat C6 glioma has been demonstrated by analysis of the hydrolysis of ATP labeled in the base and in the alpha- and gamma-phosphates. The enzyme degraded ATP into AMP and PPi and, depending on the ATP concentration, accounted for approximately 50-75% of the extracellular degradation of ATP. The association of the enzyme with the plasma membrane was confirmed by ATP hydrolysis in the presence of a varying concentration of pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), a membrane-impermeable inhibitor of the enzyme. PPADS concentration above 20 microM abolished the degradation of ATP into AMP and PPi. The nucleotide pyrophosphatase has an alkaline pH optimum and a Km for ATP of 17 +/- 5 microM. The enzyme has a broad substrate specificity and hydrolyzes nucleoside triphosphates, nucleoside diphosphates, dinucleoside polyphosphates, and nucleoside monophosphate esters but is inhibited by nucleoside monophosphates, adenosine 3',5'-bisphosphate, and PPADS. The substrate specificity characterizes the enzyme as a nucleotide pyrophosphatase/phosphodiesterase I (PD-I). Immunoblotting and autoadenylylation identified the enzyme as a plasma cell differentiation antigen-related protein. Hydrolysis of ATP terminates the autophosphorylation of a nucleoside diphosphate kinase (NDPK/nm23) detected in the conditioned medium of C6 cultures. A function of the pyrophosphatase/PD-I and NDPK in the purinergic and pyrimidinergic signal transduction in C6 is discussed. |
| Databáze: | OpenAIRE |
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