Answer:
Temperature.
Step-by-step explanation:
Just like pH, temperature also play a very important role in enzymatic activity. Enzymes are very specific to a particular temperature which is called as optimum temperature. If the temperature goes above or falls below this optimum limit, the enzymes cease to work. A lower temperature causes enzymes to become inactive while a higher temperature leads to denaturation of enzymes. In both of these situations, enzymes do not work.
For example: In our body, the optimum temperature for enzymes is 37 °C and even a small variation in optimum temperature our enzymes cease to work.