Molecular kinetics of muscle adenosinetriphosphatase. III. Influence of hydrostatic pressure.
Abstract 1. 1. An experimental study has been made of the kinetics of the myosinadenosine triphosphate system over a range of hydrostatic pressures (up to 10,000 lb./sq. in.). The work was done over a range of substrate concentrations and at three potassium chloride concentrations, namely 0.05, 0.3, and 0.6 M . 2. 2. The data have been analyzed in terms of the Michaelis-Menten mechanism of enzyme action, and volumes of activation calculated for the bimolecular interaction of enzyme and substrate and for the breakdown of the complex into products; these results are summarized in Table II. Some indication has also been obtained of the effect of KCl concentration on the kinetics. 3. 3. The results are shown to be consistent with previous hypotheses as to the nature of the enzyme-substrate interaction and of the breakdown of the complex. The volumes associated with the enzyme-substrate interaction are positive, which is consistent with there being a charge neutralization as the enzyme and substrate come together. The volumes associated with the breakdown are negative, a fact which is attributed to changes in the conformation of the enzyme. 4. 4. The data obtained for this reaction are compared with volume and entropy data for other enzyme reactions, and are found to show some features in common.