The mechanism of ATP hydrolysis catalyzed by myosin and actomyosin, using rapid reaction techniques to study oxygen exchange

J Biol Chem. 1981 Nov 10;256(21):10910-6.


During ATP hydrolysis, myosin or subfragment 1 catalyzes the exchange of oxygens between water and phosphate, so that on average, each product Pi molecule contains more than one oxygen atom derived from water. Using quenched-flow techniques, the exchange process in both ATP and Pi was studied in the rabbit skeletal muscle subfragment 1 ATPase. The exchange in protein-bound ATP (M*.ATP) and protein-bound ADP.Pi (M**.ADP.Pi) was followed as a function of time. The pattern of exchange follows closely a model in which M*.ATP + H2O and M**.ADP.Pi are interconverted directly, without any characterizable intermediate between these species. All oxygen atoms of Pi are equivalent with respect to loss to solvent, and elimination of water to re-form ATP occurs with a rate constant of 15 s-1 (at pH 8.0, I 0.015 M, 20 degrees C). This is the first direct measurement of the rate constant for the transformation of M**.ADP.Pi to M*.ATP. Oxygen exchange during steady state ATP hydrolysis in the presence of acto-subfragment 1 also fits well to this model, with actin reducing the time available for M*.ATP and M**.ADP.Pi to undergo exchange.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actomyosin / metabolism*
  • Adenosine Diphosphate
  • Adenosine Triphosphate / metabolism*
  • Animals
  • Kinetics
  • Muscles / metabolism*
  • Myosins / metabolism*
  • Oxygen Isotopes
  • Phosphates
  • Rabbits


  • Oxygen Isotopes
  • Phosphates
  • Adenosine Diphosphate
  • Adenosine Triphosphate
  • Actomyosin
  • Myosins