Abstract
SummaryA cyclic AMP-dependent protein kinase was partially purified from toad urinary bladder epithelium. Cyclic AMP-stimulated protein kinase activity as well as the unstimulated (control) activity of the enzyme was maximal at pH 6.5 using Tris-maleate, sodium cacodylate or sodium acetate buffers. The apparent Km value of cyclic AMP for the stimulation of the enzyme (in sodium acetate buffer and in the presence of 10 mM Mg2+) was 1.5 × 10-9M. The acyclic nucleotide 5'-AMP (in the concentration range 5 × 10-10 to 5 × 10-5M) failed to activate bladder protein kinase. Ca2+ was found to be inhibitory at concentrations higher than 5 × 10-4M. A role for cyclic AMP-dependent protein kinase in neurohypophyseal hormone-induced permeability changes is discussed.
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