title: Mechanism of self-phosphorylation of adenosine 3':5'-monophosphate-dependent protein kinase from bovine cardiac muscle.
abstract: The adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase purified from bovine cardiac muscle catalyzes the transfer of up to 2 mol of 32P from [lambda-32P]ATP to seryl residues in its cyclic nucleotide-binding protein component (Erlichman, J., Rosenfeld, R., and Rosen, O. M. (1974) J. Biol. Chem. 249, 5000-5003). We now present three lines of evidence to support our conclusions that the undissociated holoenzyme does not catalyze the phosphorylation of exogenous substrates but can undergo self-phosphorylation by an intramolecular reaction: (a) addition of either cAMP-binding protein or the protein kinase inhibitor (Walsh, D. A., Ashby C. D., Gonzales, C., Calkins, D., Fischer, E. H., and Krebs, D. G. (1971) J. Biol. Chem. 241, 1977-1985) does not inhibit self-phosphorylation as it does phosphorylation of exogenous substrates in the presence or absence of cAMP; (b) addition of catalytic subunit to an excess of cyclic nucleotide-binding protein results in phosphorylation equivalent to the amount of holoenzyme so generated; (c) the rate of self-phosphorylation is not affected by dilution of the holoenzyme.
mesh_terms: D000818:Animals; D002417:Cattle; D000242:Cyclic AMP / Q000494:pharmacology*; D004789:Enzyme Activation; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology*; D010750:Phosphoproteins / Q000096:biosynthesis; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*
chemical_list: D010750:Phosphoproteins; D000242:Cyclic AMP; D011494:Protein Kinases