Product release is not the rate-limiting step during cytochalasin B-induced ATPase activity of monomeric actin.

Under conditions where cytochalasin B induces ATPase activity of monomeric actin (0.3 mM MgCl2, 1 mM EGTA, 30 microns cytochalasin B, 1 mM ATP) the rate constant of the exchange of actin-bound epsilon-ATP for free ATP is about 4-6 times faster than steady state ATPase activity. When a stoichiometric ATP-actin complex is extracted with PCA (single turnover experiment) the apparent rate constant of Pi generation is not faster than steady state ATPase activity. - The experiments suggest that the hydrolysis of actin-bound ATP and not the subsequent release of hydrolysis products is rate-limiting during cytochalasin-induced ATPase activity of actin.