CHARACTERIZATION OF MULTIPLE EXTRACELLULAR CAMP-PHOSPHODIESTERASE FORMS IN DICTYOSTELIUM-DISCOIDEUM

The growth phase extracellular adenosine 3′:5′-monophosphate phosphodiesterases from Dictyostelium discoideum have been studied. Following enzyme activation with dithiothreitol and magnesium chloride (1), three peaks of activity are resolved on DEAE-cellulose chromatography. The three forms are distinct with respect to: 1) mobility on non-denaturing polyacrylamide gel electrophoresis; 2) molecular weight; 3) sensitivity to an inhibitor protein. The Michaelis constants (Km) for cAMP of all three forms are similar and in the 1-10 μM concentration range: no evidence is found for an enzyme species with a Km in the 1-10 mM concentration range or for monomer-dimer interconversion as noted by other workers (2). © 1979 Academic Press, Inc. All rights of reproduction in any form reserved.