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- Title
An Ecto-Nucleotide Pyrophosphatase Is One of the Main Enzymes Involved in the Extracellular Metabolism of ATP in Rat C6 Glioma.
- Authors
Grobben, Bert; Anciaux, Katelijne; Roymans, Dirk; Stefan, Cristiana; Bollen, Mathieu; Esmans, Eddy L; Slegers, Herman
- Abstract
Abstract : 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 α-and γ-phosphates. The enzyme degraded ATP into AMP and PPi and, depending on the ATP concentration, accounted for ~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 μM abolished the degradation of ATP into AMP and PPi . The nucleotide pyrophosphatase has an alkaline pH optimum and a K m for ATP of 17 ± 5 μM . 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.
- Subjects
PYROPHOSPHATES; GLIOMAS; CELL membranes
- Publication
Journal of Neurochemistry, 1999, Vol 72, Issue 2, p826
- ISSN
0022-3042
- Publication type
Article
- DOI
10.1046/j.1471-4159.1999.0720826.x