Enzymes are affected by the pH and temperature of their environment. For instance, stomach enzymes are meant to function in highly acidic environments. However, other enzymes have different functions, and may thrive in a lower pH. When an enzyme is exposed to a much higher or lower pH than they are made to function at, they become denatured. The same is with temperature. Exposing an enzyme to high temperature can denature it too. Hope this helps! :)