What Environmental Factors Can Enzyme Activity Be Negatively Affected By?

Whether you’re taking your first biology class or are a seasoned veteran of enzyme studies, the environmental factors that can impact the ability of enzymes to react with their substrates are important to know. In the traditional lock-and-key model, a single substrate binds to a single enzyme, catalyzing a particular reaction and causing the enzyme to form a product. This model is now outmoded and has replaced with the concept of induced fit. However, enzyme specificity for its substrate still applies.

pH Levels

An enzyme loses its ability to function when it loses its shape. Because ionic and hydrogen bonds are important factors in enzymes retaining their specific shapes, pH levels that interrupt this bonding, negatively impact enzyme activity. In a study conducted at the College of DuPage, for instance, hydrogen peroxidase from cow operated most efficiently at a neutral pH of 7. Activity was quite low at a pH of 11, and nonexistent at a pH of 1. Extreme pH levels may also impact the substrate or its bonds, hindering the ability of the substrate to react with the enzyme, causing a further decrease in activity.

Temperature Levels

Temperature levels also play an important role in how effectively enzymes function. In the same College of DuPage study, the hydrogen peroxidase functioned most effectively at 41 degrees Celsius, a temperature which caused molecules to move quickly and bond with one another more rapidly. Very high temperatures, however, run the risk of denaturing enzymes by destroying their bonds and their shapes. Low temperatures, on the other hand, can cause enzymes to slow down and decrease their rate of interaction with substrates.

Enzyme Inhibitor Presence

A class of chemicals that interrupt the proper binding of substrates to enzymes are known as inhibitors. They either slow down the process, or they can stop it altogether. Inhibitors in the enzyme’s environment can change its shape so that a substrate no longer fits to it, a process called noncompetitive inhibition. Competitive inhibition, on the other hand, is when a nonsubstrate chemical takes on a shape similar to a substrate, and “fits” into the binding site on the enzyme instead of the actual substrate. This too blocks real reactions.

Substrate Concentration

Substrates, as the “key” that unlocks enzyme activity, have a significant effect on how efficiently enzymes function. Higher substrate concentrations will increase an enzymes activity, simply because more substrate present means more substrate available for binding. At low substrate concentrations, increases in substrate concentration result in a steep increase in enzyme activity. At very high substrate concentrations, however, the increase in enzyme activity flattens out, and, at very high concentrations, no increase in enzyme activity will be realized with an increase in substrate concentration.