Diastereomers of adenosine 3',5'-monothionophosphate (cAMP[S]) antagonize the activation of cGMP-dependent protein kinase.
cGMP-dependent protein kinase contains four cGMP-binding sites which are homologous to the four cAMP-binding sites of cAMP-dependent protein kinase. The interaction of the diastereomers of adenosine 3',5'-thionophosphate, (PS)-cAMP[S] and (PR)-cAMP[S], with cGMP-dependent protein kinase has been studied. Autophosphorylation of cGMP-dependent protein kinase is stimulated by cAMP and (PS)-cAMP[S] with apparent KA values of 7 microM and 94 microM, respectively. cAMP-stimulated autophosphorylation is inhibited competitively by (PR)-cAMP[S] with a Ki value of 15 microM. The phosphorylation of the peptide substrate (Leu-Arg-Arg-Ala-Ser-Leu-Gly) is stimulated by cGMP (approx. KA 1 microM) and cAMP (approx. KA 98 microM) but neither by the (PR) nor (PS) stereoisomer of cAMP[S]. (PR)-cAMP[S] and (PS)-cAMP[S] inhibit competitively cAMP-or cGMP-stimulated phosphorylation of the peptide substrate with Ki values of 52 microM and 73 microM, respectively. (PS)-cAMP[S] stimulates the phosphorylation of the peptide substrate by an autophosphorylated enzyme. Binding of [3H]cGMP to cGMP-dependent protein kinase is inhibited by (PS)-cAMP[S] and (PR)-cAMP[S] with IC50 values of 200 microM and 15 microM, respectively. These results show that both diastereomers of cAMP[S] bind to cGMP-dependent protein kinase. (PR)-cAMP[S] has properties of a pure antagonist whereas (PS)-cAMP[S] has properties of a partial agonist. The results provide further evidence that autophosphorylation of the enzyme affects the interaction between the cGMP-binding sites and the catalytic center of the enzyme by facilitating the activation of the phosphotransferase reaction.
Hofmann
F
F
Gensheimer
H P
HP
Landgraf
W
W
Hullin
R
R
Jastorff
B
B
D001667:Binding, Competitive; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D013237:Stereoisomerism; D013873:Thionucleotides / Q000378:metabolism / Q000494:pharmacology*
D010455:Peptides; D047428:Protein Kinase Inhibitors; D013873:Thionucleotides; C016957:adenosine-3',5'-cyclic phosphorothioate; D000242:Cyclic AMP; D011494:Protein Kinases