Mechanism of the bell-shaped profile of ribonuclease a activity: molecular dynamic approach.

Ribonuclease-A is a small enzyme contains an active site with positive charges for its substrate. His(12) and His(119) of its active site play critical role in enzyme catalysis. Salts show a bell-shaped profile on enzyme activity with an optimum salt concentration of about 0.1 M for optimum activity. The mechanism of decreased activity of the enzyme at low salt concentrations is not clear. In this work, we made a new effort to study the molecular events causing inactivation of RNase-A at low concentrations of NaCl. Our molecular dynamic result confirms that decrease in salt concentrations below an optimal level leads to an enzyme structure with lower dynamism and flexibility than that needed for optimum activity.