title: Stimulation of adenylate cyclase by Ca2+ and calmodulin in rat islets of langerhans: explanation for the glucose-induced increase in cyclic AMP levels.
abstract: The effect of Ca2+ and calmodulin has been studied on adenylate cyclase activity in homogenates of rat islets of Langerhans. EGTA had a stimulatory effect on the enzyme in accord with the known inhibitory effect of Ca2+. In contrast, the addition of Ca2+ together with calmodulin is stimulatory and demonstrates the existence of a Ca2+-dependent adenylate cyclase in islets of Langerhans. It is suggested that the glucose-induced increase in cyclic AMP concentrations in intact islets is a secondary consequence of the glucose-induced increase in cytosol free-Ca2+ concentrations which, with calmodulin, causes an increase in the activity of adenylate cyclase.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D007515:Islets of Langerhans / Q000201:enzymology*; D008297:Male; D051381:Rats; D013268:Stimulation, Chemical
chemical_list: D002135:Calcium-Binding Proteins; D002147:Calmodulin; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D005947:Glucose; D002118:Calcium