title: Evidence for an adenylate-cyclase activity in neurosecretory granule membranes from bovine neurohypophysis.
abstract: Purified bovine neurosecretory granules and their corresponding membranes were prepared after fractionation and purification processes from bovine pituitaries. An adenylate cyclase activity was detected both in the granules (apparent Km = 0.5 mM) and the corresponding preparations of the membranes (apparent Km = 0.5 mM). This enzyme was activated by fluoride in a way markedly dependent on the concentration of this ion, and with a maximum for a concentration of F- = 3.5 mM. The cyclase activity was also significantly enhanced by GTP. The reaction rate showed a strong dependence on the molar ration [Mg2+]/[ATP] with maximal velocity for 7. It is suggested that this activity might play an important role in the control and regulation of neurosecretion in the neurohypophysis.
mesh_terms: D000262:Adenylyl Cyclases / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D003594:Cytoplasmic Granules / Q000201:enzymology / Q000648:ultrastructure; D004789:Enzyme Activation; D005260:Female; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008566:Membranes / Q000201:enzymology / Q000648:ultrastructure; D008854:Microscopy, Electron; D009490:Neurosecretory Systems / Q000201:enzymology*; D010904:Pituitary Gland, Posterior / Q000201:enzymology*
chemical_list: D000262:Adenylyl Cyclases; D008274:Magnesium