Triton X nonionic surfactants reversibly inhibit the [formula omitted] ATPase activity of myosin

Abstract

The nonionic octylphenoxy polyethoxy series of surfactants, Triton X, reversibly inhibited the EDTA KCl ATPase activity of purified rabbit skeletal muscle myosin at concentrations at or below their reported critical micelle concentrations. The maximum degree of enzyme inhibition increased with ethoxy content to 88% (with Triton X 102 average ethoxy content, 12.5 per molecule). The results suggest that binding of the surfactant to the myosin molecule occurs below the critical micelle concentrations and that the hydrophilic ethoxy chain forms a diffusion barrier against approach of ATP to the enzyme's active site. This model has implications for the organization of myosin in the plasma membrane of phagocytes.