[Inhibition of nonenzymatic ATP hydrolysis by its binding with the cationic detergent micelles]

The rate of ATP hydrolysis is shown to decrease sharply by its binding with mycelles formed from cetyltrimethyl ammonium bromide (CTAB) (pH 9.0, 20 degrees C). Under these conditions only trace amounts of hydrolytic products have been found in the reaction mixture after a two-months standing. In the absence of mycelles the ATP hydrolysis is practically completed in 7 days. The energies of ATP, ADP and Pi binding with mycelles and at the interface of the "octane - water" system with previously adsorbed CTAB have been measured. The estimates demonstrate that the binding of one negative charge of phosphate anion or that of nucleotides with CTAB at the interface of the "octane - water" system corresponds to the change in free energy, i.e. -3.5 ccal/mol. The sharp deceleration of ATP hydrolysis cannot be due to the shift in the equilibrium of ATP hydrolysis reaction towards the formation of the pyrophosphate bond under conditions when all reaction components are bound to the surface of the mycelles.