When an enzyme's activity is destroyed by heat or a change in ph, the enzyme is said to be select one:

a. broken.

b. toxic.

c. conjugated.

d. tertiary.

e. denatured?

It is said to be E, denatured.

Each type of enzyme has its own optimum pH value and temperature, such as pH 7.0 and 37°C for amylase. In this optimum pH level or temperature, or some range close to this level, the enzyme works the fastest. However, if the pH value gets too extreme, or the temperature gets too high, the enzyme would denature, which means, the active site of the enzyme would be altered and will lose their 3 dimensional shape, which also means, it can no loner bind into substrates and they no longer work, no matter how you fix the temperature or the ph of the environment.

Note that if the temperature gets too low, the enzyme would not be denatured, just inactive, but once you raise the temperature back to its optimum temp, it'll work normal.