The most common four factors affecting enzyme activity are enzyme concentration, substrate concentration, pH and temperature, and inhibitors and activators. In addition, it is important to note that these factors will affect the rate of the enzymatic reaction but the reaction rate will not necessarily affect the activity. In this sense, some experts argue that the first two factors shouldn’t be counted.
If this factor is consistent, the increasing concentration of substrates, the molecules involving the reaction, will influence the rate at which enzymatic reactions proceed. As the concentration of substrate increases, the rate of initial reaction will increase accordingly as more enzyme promotes the reaction. However, after reaching a certain point the added substrates won’t affect the activity anymore since the quantity of enzyme is limited. In this case, the reaction rate will remain the same because the extra substrates have to wait for an enzyme to promote the reaction.
When substrate is in a lower concentration range, the increasing concentration will promote the rate of substrate binding to the enzyme. That’s to say, the enzymatic reaction will thus become faster.
PH and temperature
Many enzymes work only within a very narrow range of pH values. Once they find themselves in unsuitable pH range, they will denature. In fact, the ideal pH range for many is from 7 and 7.5. Mind you, it doesn’t make sense to all of them. Some like gastric enzymes are most efficient at an acidic pH of 1.5 while the others like intestinal ones work best at alkaline pH of 8.0
Temperature is one of the main factors that affect enzyme activity. When the temperature increases, the molecule will usually move faster and faster, which means that the molecules are more likely to collide with them. However, the higher collision rate can only increase the reaction to some extent. If the temperature keeps rising, the enzyme protein will begin to denature. For many of them, the optimum temperature ranges between 25 to 40 degrees Celsius. But the exceptional ones are some animals living in the sea or hot springs. They tend to have some enzymes that can have higher or lower optimal survival temperature.
Inhibitors and activators
They can be divided into three categories.
1. Competitive inhibitors. They impact the binding efficiency of enzyme and substrate by competing with substrate for the active site;
2. Anti-competitive inhibitors. They combine with the complex of substrate and enzyme, prevent the formation of the product, and then affect the production rate. In fact, you can also think that the changed structure of enzymes causes the decrease of the enzymatic reaction rate;
3. Non-competitive inhibitors. They incorporate with enzymes and their complex with substrate to reduce the rate of enzymatic reactions. Activator can change a non-active enzyme precursor (zymogen) to become an active one, or induce the activation by accelerating the reaction rate.