Effects of Ca2+ and calmodulin on cyclic nucleotide metabolism in neurosecretosomes isolated from ox neurohypophyses.
In neurosecretosomes, isolated from ox neurohypophyses, both guanylate and adenylate cyclase activity was shown to be predominantly membrane-bound. Membrane-bound adenylate cyclase was inhibited by increasing the ionized calcium concentration from 10(-7) M to 10(-5) M, but was stimulated by calmodulin in the presence of 10(-7) M and 10(-5) M ionized calcium. In contrast, neither calcium ions nor calmodulin affected the activity of membrane-bound guanylate cyclase. Soluble cyclic AMP and cyclic GMP phosphodiesterase activities increased with increasing ionized calcium concentration (10(-7) M to 10(-3) M). At 10(-7) M ionized calcium concentration, both soluble phosphodiesterase activities were stimulated by calmodulin. Both the membrane-bound phosphodiesterase activities were inhibited by a high ionized calcium concentration (10(-3) M) and not affected by calmodulin.
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism*; D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000378:metabolism*; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D004789:Enzyme Activation; D006162:Guanylate Cyclase / Q000378:metabolism*; D007700:Kinetics; D010904:Pituitary Gland, Posterior / Q000201:enzymology*; D013347:Subcellular Fractions / Q000201:enzymology
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase; D002118:Calcium