[The electrostatic contribution to interactions of some enzymes with polyelectrolytes]

To explain the inhibitory action of polyelectrolytes on enzymes and, in particular, to define potentially reactive zones for the binding of polyelectrolyte, the electric potential of enzymes lactate dehydrogenase and glutamate dehydrogenase was calculated using the solution of the Poisson-Boltzmann equation by a numerical method with the use of the Gauss-Seidel relaxation method at three pH values: 6.5, 7.0, and 8.0 and three values of ionic strength: 50, 100, and 150 mm. On the basis of these calculations and their visualization, representative sites for favorable binding of polyanions were determined as extended areas on the surface of proteins with the positive potential in the neutral pH region. It was shown that there is a correlation between the area of positive potential and the efficiency of enzyme inactivation for a number of pH values and concentrations of salt for two enzymes. The calculations performed allowed one to explain the inhibitory action of polyelectrolytes on the specified enzymes to understand the difference between the values of polyelectrolyte inactivation constants for the two enzymes and estimate the minimal areas of the positive potential on the protein surface that provide their effective inhibition.