Phosphorylation of cardiac troponin by guanosine 3':5'-monophosphate-dependent protein kinase.
Homogeneous cGMP-dependent protein kinase catalyzes the rapid incorporation of phosphate, specifically into the inhibitory subunit of purified cardiac troponin with a maximal incorporation of 1 mol of phosphate/mol of troponin. When troponin was incubated in the presence of both cGMP- and cAMP-dependent protein kinases, a maximal incorporation of 1 mol of phosphate/mol of troponin was observed which suggested phosphorylation of the same site by the two kinases. Both cyclic nucleotide-dependent kinases had similar Km values for troponin, but the Vmax value for the phosphorylation reaction catalyzed by cAMP-dependent protein kinase was 12-fold greater than the value obtained for cGMP-dependent protein kinase.
D000818:Animals; D002417:Cattle; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology*; D004789:Enzyme Activation; D007700:Kinetics; D008168:Lung / Q000201:enzymology; D009124:Muscle Proteins; D009206:Myocardium; D011494:Protein Kinases / Q000378:metabolism*; D014336:Troponin
D009124:Muscle Proteins; D014336:Troponin; D000242:Cyclic AMP; D011494:Protein Kinases; D006152:Cyclic GMP