KINETIC CONSTANTS OF THE INTERACTION BETWEEN MYOSIN AND ADENOSINETRIPHOSPHATE

Abstract

Using the previously developed methodology of following the the free ATP concentration in a multienzyme system composed of myosin with a rephosphorylating enzyme and a reservoir substrate, or with myosin only, we have determined-individual kinetic constants for myosin-ATPase; k1= 2.1 x 104, k3 = 2.57x 10-2 and KA= 1.25 x 10-6 It is derived that KA is practically equal to k3/k4 and is, therefore, not an equilibrium constant. The standard free energy effect of the binding reaction is, therefore'', even greater than would be the case if the Michaelis constant were an equilibrium constant, and exceeds a value of 11,000 calories per mole. It is further derived that the effect of ATP upon dissolved actomyosin is due to its binding, not to its splitting, but no data are available to analyze this question for the case of the contraction of actomyosin systems.