[Characterization of cyclic AMP-dependent protein kinase from smooth muscle of cattle and its modification by drugs].

Cyclic AMP-dependent protein kinase activity (ATP: protein phosphohydrolase, EC 2.7.1.37) from the postmicrosomal supernatant (100 000 X g supernatant) of bovine coronary and carotid arteries was isolated by ammonium sulfate precipitation followed by ion-exchange chromatography on DEAE-cellulose and partially characterized. Kinase activity was assayed in a standard system with [gamma-32P]-ATP and protamine at pH 7.5, 310 K, in the presence and absence of cyclic AMP. The apparent Km-values for ATP, Mg2+ and cAMP are 6.1 X 10(-5) M, 6.4 X 10(-4) M, 3.4 X 10(-8) M, respectively (coronary arteries) or 5.0 X 10(-5) M, 1.02 X 10(-3) M, 1.7 X 10(-8) M, respectively (carotids). Optimal concentrations of cAMP produced a 2-3-fold increase in the cyclic AMP-dependent protein kinase activity. After purification on DEAE-cellulose three peaks of cyclic AMP-dependent protein kinase activity were found. Especially the second peak fraction showed high protein kinase activity, strong [3H]cAMP-binding and high sensitivity to cAMP. Several drugs tested on the crude enzyme preparation showed stimulating or inhibitory activities in the concentration range of 1-10 microM.