title: A study of the 18O-exchange reactions catalyzed by cardiac myosin and its subfragment 1.
abstract: Isotope-exchange reactions (H2(18)O in equilibrium with KH2PO4) during ATP hydrolysis catalyzed by myosin and its subfragment 1 from rabbit, dog, and human cardiac muscle were studied. All preparations of myosin and subfragment 1 in the presence of Mg2+ catalyzed two types of 18O-exchange reactions similar to those of skeletal muscle: intermediate and direct 18O exchange. The dependences of both reactions on divalent metals and nucleotides were studied. Data on 18O exchange of subfragment 1 from rabbit, dog, and human cardiac muscle were obtained for the first time. They indicate the similarity of molecular mechanisms of ATP energy use in cardiac and skeletal muscle contraction.
mesh_terms: D000205:Actomyosin / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D004285:Dogs; D004734:Energy Metabolism; D006801:Humans; D008274:Magnesium / Q000378:metabolism; D009200:Myocardial Contraction; D009206:Myocardium / Q000201:enzymology*; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D010101:Oxygen Consumption; D010446:Peptide Fragments / Q000378:metabolism*; D011817:Rabbits
chemical_list: D015879:Myosin Subfragments; D010446:Peptide Fragments; D000255:Adenosine Triphosphate; D000205:Actomyosin; D000251:Adenosine Triphosphatases; D009218:Myosins; D008274:Magnesium