Adenyl Cyclase of Rat Cerebral Cortex

Sodium fluoride activates adenyl cyclase at a rate that is dependent on temperature and the concentration of NaF.The activation is not readily reversed by dilution, extensive washing of the membrane-bound enzyme, or dialysis.Activation occurs in the absence of added Mg++, but the rate of activation is increased Z-fold by 5 mM Mg++.The NaFactivated enzyme is more stable at 40" and during dialysis than the native enzyme.The enzyme also is activated by Triton X-100 and to a lesser extent by sodium dodecyl sulfate.The activity of the detergent-treated enzyme is not stimulated by NaF, but the activity of the NaF-activated enzyme can be increased by Triton X-100.Thus, NaF does not cause full expression of adenyl cyclase activity.Freezing and thawing of the cerebral cortex of young (1 to 20 days) rats prior to homogenization causes a 2-fold increase in enzyme activity.It was concluded that adenyl cyclase exists in its membranous environment in a state of inhibition.Treatment with detergents or freezing of the tissue could lead to nonspecific changes in membrane structure which cause reduction of the inhibition and increased catalytic activity.