The Endometrial Adenosine Cyclic 3′:5′-Monophosphate-dependent Protein Kinase

Bovine endometriumhas been shown to possess an adenosine cyclic 3':5'-monophosphate (CAMP)-dependent protein kinase which is located almost exclusively in the cytosol.Purified enzyme could be separated into a specific CAMPbinding fraction and an activated protein kinase in the presence of CAMP on diethylaminoethyl-cellulose and casein-Sepharose.The isolated subunits could be recombined to form the CAMP-dependent protein kinase.Equilibrium studies at pH 5.0 indicated one major class of binding site for both the intact protein and the isolated binding subunit, but a higher association constant for the CAMP-binding subunit.Dissociation of [3H]cAMP from the binding protein-CAMP complex in the presence or absence of kinase subunit obeyed first order kinetics and exhibited temperature dependence.The association reaction of binding subunit and CAMP exhibited second order kinetics and was temperature dependent, but the association rate constant varied negatively with the initial concentration of CAMP.When the intact enzyme was employed, second order plots were no longer linear under conditions of equimolar CAMP-binding sites and CAMP and were not temperature dependent.Under pseudo-first order conditions, however, the rate constants approximated those obtained with the binding subunit.These data showed that the presence of the kinase subunit could affect both the association rate and the equilibrium concentration of the binding subunit-CAMP complex under second order conditions.The uterus serves as a target for a variety of hormones.The interplay of hormonal action is reflected in uterine capacity for