[Influence of dinitrophenol, octanol and toluene upon pH-dependence of ca-ATPase activity of heavy meromyosin].

It is found that dinitrophenol, octanol and toluene produce similar effects on pH-dependence of ATPase of myosin and heavy meromyosin (HMM), i.e. they decrease or remove the neutral suppression of ATPase activity. The appearance of pH-dependence curves is simplified and approaches the form, which is characteristic for the ionisation curve of one; in the last resort two groups, participating in the enzyme activity. The activity of HMM is higher and the zone of the neutral suppression is diminished at low ionic strength, the activation by the modifiers being observed at the significantly lesser degree. CaATPase activation by dinitrophenol, octanol and toluene is suggested to be of the same nature and is accounted for the masking of "the inhibiting" ionizable group of the enzyme with near to neutral pK. This masking may be the result of the conformational changes occuring at the deformation of hydrofobic regions. The ionization of "the activity inhibiting" group of the enzyme depends directly or indirectly on the concentration of potassium chloride and the increase of KCl concentration bring to the inhibition of ATPase activity.