title: Studies of fluoride-preactivated rabbit liver adenylyl cyclase.
abstract: Rabbit liver adenylyl (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) cyclase was stimulated by preincubation with F- and Mg2+ and the stimulation persisted despite extensive washing and/or detergent solubilization. Optimum preactivation conditions were found to be 4 mM NaF and 2 mM MgCl2; higher or lower concentrations produced submaximum stimulation regardless of preincub ation time. In addition to an enhanced catalytic acticity, the activated enzyme also exhibited different responses to Ca2+ and Cu2+ when compared to the basal enzyme. ATP caused a time-dependent inhibition that could be partially prevented or reversed by F-, but was not completely reversed by washing. This inhibition was not observed when 5'-adenosine(beta, gamma-imide) triphosphate blocks inhibition by ATP. The results support, but do not prove, the proposed molecular basis of F- activation which entails a phosphorylation-dephosphorylation mechanism.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000818:Animals; D004789:Enzyme Activation; D005459:Fluorides / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D010766:Phosphorylation; D011817:Rabbits; D013329:Structure-Activity Relationship
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D000266:Adenylyl Imidodiphosphate; D000255:Adenosine Triphosphate; D000262:Adenylyl Cyclases; D008274:Magnesium; D005459:Fluorides