Once the reaction is complete the enzyme remains the same but the substrate transforms to products. What word describes the pH at which the speed. Protein The Mechanism Of Enzymatic Action Britannica The change in shape activates the substrate molecule and decreases the total activation energy required for the substrate to be turned into product. . Enzymes are potent catalysts. In other words the enzyme reacts with the substrate forming an enzyme-substrate complex. What word describes the pH at which the speed of a reaction involving an enzyme occurs best. Changes in pH may not only affect the shape of an enzyme but it may also change the shape or charge properties of the substrate so that either the substrate cannot bind to the active site or it cannot undergo catalysis. The catalase activity experimental procedure o Negative Control What word describes The loss of an enzymes original shape and ability of its active. In t...