title: Inhibition of bovine adrenocortical adenylate cyclase activity by adenosine.
abstract: Incubation of bovine adrenocortical membranes with corticotropin and 5-guanylylimidodiphosphate produced a state of adenylate cyclase (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) with maximal catalytic activity and an increased sensitivity to inhibition by adenosine. Due to metabolism of adenine nucleotides during adenylate cyclase assays a quantitative assessment of the nature of this inhibition was not possible. However, when determined at 0.2--1.0 mM MgATP2-, half-maximal inhibition of the basal and maximally active states of the enzyme was observed at adenosine concentrations of 210--330 and 70--90 micrometer, respectively. The inhibition appeared to be partially competitive, suggesting that the nucleoside may act as an allosteric negative effector which reduces the affinity of the active site for substrate. Adenosine was 5--6 times more potent as an inhibitor of adrenal adenylate cyclase than 2-chloroadenosine. Adenosine deaminase abolished the inhibitory effect of the nucleoside, whilst theophylline had no effect on activity either in the absence or presence of adenosine.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D000243:Adenosine Deaminase / Q000494:pharmacology; D000067956:Adenylyl Cyclase Inhibitors; D000302:Adrenal Cortex / Q000201:enzymology*; D000310:Adrenal Gland Neoplasms / Q000201:enzymology; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D009374:Neoplasms, Experimental / Q000201:enzymology
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D000243:Adenosine Deaminase; D000241:Adenosine