title: Decrease in calcium transport associated with phosphoprotein phosphatase-catalyzed dephosphorylation of cardiac sarcoplasmic reticulum.
abstract: Phosphoprotein phosphatase activity is found in preparations of sarcoplasmic reticulum isolated from canine heart when assayed with either phosphate or phosphorylated sarcoplasmic reticulum as substrate. Phosphoprotein phosphatase-catalyzed dephosphorylation of the 22,000 dalton phosphoprotein of cardiac sarcoplasmic reticulum is stimulated markedly by MnCl2 (5 mM) and to a lesser extent by MgCl2 (5 mM); inorganic phosphate (50 mM) and NaF (25 mM) are inhibitory. Dephosphorylation of this 22,000 dalton phosphoprotein is correlated with a decreased initial rate of calcium transport. The close structural and functional relationship of phosphoprotein phosphatase to the cardiac sarcoplasmic reticulum suggests a possible role of this enzyme in reversing the relaxation-promoting effects of catecholamines on the intact heart.
mesh_terms: D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D004285:Dogs; D004492:Edetic Acid / Q000494:pharmacology; D005459:Fluorides / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism / Q000648:ultrastructure; D010750:Phosphoproteins / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism*; D012995:Solubility
chemical_list: D010750:Phosphoproteins; D008345:Manganese; D011189:Potassium Chloride; D004492:Edetic Acid; D010744:Phosphoric Monoester Hydrolases; D008274:Magnesium; D005459:Fluorides; D002118:Calcium