The ATPase reaction in the steady state and in the initial burst catalyzed by chicken gizzard myosin in 0.6 M KCl1.

On studying the steady-state activity in 0.6 M KCl, it was found that Mg-ATPase of chicken gizzard myosin was identical with that of rabbit skeletal myosin in the pH-activity profile, Michaelis-Menten constant, and maximum velocity. As regards the "initial burst" of ATP splitting in the presence of Mg (0.6 M KCl), it was found that gizzard and skeletal myosins were identical both in the size of the initial burst and in the velocity-ATP concentration relationship. The only difference we observed was that the Ca- and EDTA-ATPase activities of gizzard myosin were, as reported by other investigators, approximately one-half to one-third of those of skeletal myosin, although the pH-activity profiles for the ATPase of gizzard myosin was essentially the same as that of skeletal myosin.