Conformational dynamics of protein side chains and enzyme-substrate interaction

The electric interaction of charged and polar protein side chains with dipole moments of the bonds of substrate molecules bound in enzyme active sites is considered. The conformational motion of the side chains leads to the fact that the electric interaction, besides a constant (electrostatic) part, contains a fluctuating one, which is a random force (noise) exerted on the substrate molecule. On the time scale of enzyme turnovers this noise can be considered as the white one with good approximation. The noise is external, and the explicit expression for its intensity has been obtained. The possible functional role of the noise as an activating factor in enzyme catalysis is discussed.