We compared the properties of the ectonucleotidases (nucleoside triphosphatase, EC 188.8.131.52; nucleoside diphosphatase, EC 184.108.40.206; 5′-nucleotidase, EC 220.127.116.11) 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′-[β-thio]triphosphate, but not of adenosine 5′-[α-thio]triphosphate, by the triphosphatase and stereoselective catabolism of adenosine 5′-[α-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.
Research Article|September 01 1985
Characterization of ectonucleotidases on vascular smooth-muscle cells
Biochem J (1985) 230 (2): 503-507.
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J D Pearson, S B Coade, N J Cusack; Characterization of ectonucleotidases on vascular smooth-muscle cells. Biochem J 1 September 1985; 230 (2): 503–507. doi: https://doi.org/10.1042/bj2300503
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