How do temperature and pH affect the activity of this enzyme?

hmm....enzymes placed in solutions that are non-ideal...for example, either too hot, too cold, or at too high/low a pH will ultimately be denatured (H-bonds will be broken, and the shape and structure of the protein will change, making it no longer able to perform its previous function)

Enzymes are temperature and pH specific. You did not say which one you were working with.
In the stomach the enzyme works in an acid environment.
In the small intestine it does not.
Enzymes like body temperature. Too cool they do not work. Too hot and they are denatured.

For enzymes, the structure fits the function. Enzymes are commonly referred to with 'lock and key' diagrams, where the enzyme can catalyze only one specific type of reaction. High temperature affect the structure of the enzyme and can denature the enzyme, making it unable to perform it's function, same with acidic pH's.
To define, in case you are unsure: Enzymes make easier, and faster reactions. They are the intermediate step. Example, there is a protein A and a protein B, they both stick to the enzyme, which mashes them together to make protein C. Imagine the specific shapes of the two starting proteins, and the proteins fitting into the shapes perfectly, kind of like the little kid's toy. Well, when an enzyme is exposed to high temperature, or acidic pH, the perfect shape is, essentially, ruined, and it can not catalyze, or help in, any more reactions.