Demonstration in Aspergillus niger of adenyl cyclase, a cyclic adenosine 3′,5′-monophosphate-binding protein, and studies on intracellular and extracellular phosphodiesterases

Abstract

Aspergillus niger was found to possess adenyl cyclase, one or more cyclic adenosine 3′,5′-monophosphate (cAMP) binding proteins, and two apparently distinct cAMP phosphodiesterases, one intracellular (I-PDE) and the other extracellular (E-PDE). All these activities except E-PDE were located in the soluble fractions of the cells. The I-PDE was partially purified by protamine sulfate treatment, ammonium sulfate precipitation, ethanol precipitation, and DEAE-cellulose chromatography. The I-PDE had a pH optimum of 7.5, was activated by magnesium ions, and was inhibited by EDTA. The K_m for cAMP was 2.5 mM, and for cyclic guanosine 3′,5′-monophosphate (cGMP), 0.5 mM. The E-PDE had a pH optimum of 3.5 and was inactive at pH 7.5. The K_m for cAMP was 18 μM. Preliminary evidence was obtained that the activity of the E-PDE may be regulated by endogenous inhibitor.