title: Characterization of ectonucleotidases on vascular smooth-muscle cells.
abstract: We compared the properties of the ectonucleotidases (nucleoside triphosphatase, EC 3.6.1.15; nucleoside diphosphatase, EC 3.6.1.6; 5'-nucleotidase, EC 3.1.3.5) in intact pig aortic smooth-muscle cells in culture with the properties that we previously investigated for ectonucleotidases of aortic endothelial cells [Cusack, Pearson & Gordon (1983) Biochem. J. 214, 975-981]. In experiments with nucleotide phosphorothioate diastereoisomers, stereoselective catabolism of adenosine 5'-[beta-thio]triphosphate, but not of adenosine 5'-[alpha-thio]triphosphate, by the triphosphatase and stereoselective catabolism of adenosine 5'-[alpha-thio]diphosphate by the diphosphatase were found, as occurs in endothelial cells. In contrast with endothelial ecto-5'-nucleotidase, the smooth-muscle-cell enzyme catabolized adenosine 5'-monophosphorothioate (AMPS) to adenosine: the affinity of the enzyme for AMPS was greater than for AMP, and Vmax for AMPS was about one-sixth that for AMP. In both cell types AMPS was an apparently competitive inhibitor of AMP catabolism by 5'-nucleotidase. The relative rates of catabolism of nucleotide enantiomers in which the natural D-ribofuranosyl moiety is replaced by an L-ribofuranosyl moiety were similar to those in endothelial cells. No ectopyrophosphatase activity was detected in smooth-muscle cells, in contrast with endothelial cells, where modest activity is present.
mesh_terms: D015720:5'-Nucleotidase; D017766:Acid Anhydride Hydrolases; D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000031:analogs & derivatives / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000201:enzymology*; D043583:Nucleoside-Triphosphatase; D009708:Nucleotidases / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D013552:Swine; D013873:Thionucleotides / Q000378:metabolism
chemical_list: D013873:Thionucleotides; C014308:adenosine 5'-phosphorothioate; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D009708:Nucleotidases; D010744:Phosphoric Monoester Hydrolases; D015720:5'-Nucleotidase; D017766:Acid Anhydride Hydrolases; D043583:Nucleoside-Triphosphatase; C023837:nucleoside-diphosphatase