payment page
Due to the specificity of enzymes to individual reactions and substrates, changes to molecular structure of the enzyme often results in a change of the function or efficiency of the system. Changes in protein structure are called denaturation. This can happen to enzymes through a variety of mechanisms and eliminates the ability of the enzyme to catalyze reactions. In some cases, enzyme denaturation is reversible, allowing the enzyme to regain activity.
Temperature and pH
Proteins are affected by both temperature and pH. An everyday example of this is cooking a piece of meat. When temperature or acid is applied, the proteins are denatured and their structures change. Similarly, enzymes are affected by temperature and pH. Environmental temperatures and pH outside the optimal range for a given enzyme will lead to changes in its structure, altering the efficiency with which it catalyzes reactions. Environmental temperatures can also increase the rate of reaction. When temperatures are higher, molecules move faster in a solution. This increases the frequency of collisions between enzymes and substrates and therefore increases the reaction rate. The converse is also true, as lower temperatures decrease the reaction rate. However, too much heat can lead to the denaturation of the enzyme. This loss of 3D conformation means the enzyme can no longer perform its function. pH can also cause denaturation. pH is a value that describes the relative amount of hydrogen ions in a solution. The more hydrogen ions, the more acidic. The less hydrogen ions, the more basic. This is represented by the equation: \(pH = -log[H+]\). Because of this, pH can interfere with the hydrogen bonds that help a protein maintain its shape.
Concentrations
Both the concentrations of enzymes and the relative concentrations of substrates and products determine how efficiently an enzymatic reaction proceeds. If sufficient amounts of substrate are present, increasing the concentration of enzymes can result in more reactions occurring during a given period of time. Additionally, higher concentrations of substrate increase the chances of a substrate molecule binding with an enzyme. Once all enzymes are bound to substrate molecules, the environment is considered saturated and reaction rates will stabilize.
Inhibitor Molecules and Allosteric sites
Competitive inhibitor molecules bind reversibly or irreversibly to the active site of an enzyme. These molecules are similar enough to the substrate in shape that they can bind to the active site and prevent the substrate from binding. Since enzymes have very specific active sites, competitive inhibitors often target a single enzyme. Noncompetitive inhibitor molecules bind to allosteric sites on the enzyme, which are sites other than the active site. This binding changes the shape of the enzyme, which subsequently leads to changes in its activity. Cells can use both of these mechanisms to control cell processes by blocking specific enzyme-catalyzed reactions.
