Some aspects of the influence of hydrostatic pressure on reactions catalysed by enzymes

Abstract

1. 1. Hydrostatic pressures influence enzymatic reactions in three ways: a. Low pressures accelerate the rate of enzymatic reaction. b. Relatively higher pressures slow-down the reaction rate without totally denaturing the enzyme. c. Very high pressures arrest the evolution of enzymatic reactions, inactivating the enzyme. 2. 2. It has been seen that in conditions of excess of substrate, ΔV=−13.7 ml./mole for the hydrolysis of denatured serum albumin by trypsin. For the same system ΔV in conditions of nonexcess of the Substrate=−2.9 ml./mole. 3. 3. The acceleration of enzymatic reaction under low pressures is then due to the fact that the process of activation of the complex taking place with a diminution of volume is favored under pressures of this order. When the value of pressure applied increases, the formation of the complex ES is inhibited, and we thus observe an overall slowing down of the reaction rate. 4. 4. Very high pressures inactivate the molecule of enzyme. This denaturation is different from the denaturation caused by heating, as evidenced by immunochemical assays. 5. 5. From the effects of pH on the influence of pressure on the reaction starch-amylase, it is deduced that the molecule of salivary amylase carries a negative charge in its active state. The high denaturing pressures will be acting on a reversibly inactive form of the amylase in constant equilibrium with the active form.