A kinetic study of the energy storing enzyme-product complex in the hydrolysis of ATP by heavy meromyosin

Abstract

The hydrolysis of ATP by heavy meromyosin was studied by means of the measurement of the development of enthalpy. The results were compared with the rate of change in the intensity of the ultraviolet difference spectrum of heavy meromyosin. It is shown that as far as the enthalpy change is concerned: (1) most of the excess energy associated with ATP does not directly dissipate into the solution during the rapid hydrolysis of ATP in the initial stage of the reaction but is stored in stable form in an enzyme-product complex, (2) the ultraviolet difference spectrum of heavy meromyosin is due specifically to the reaction via the enzyme-product complex, suggesting that a local conformation of heavy meromyosin is changed because of the excess energy stored in the complex, and (3) the complex dominantly exists during the steady splitting of ATP.