Here's why:

* Location: Pepsin is found in the stomach, which has a very acidic environment (pH 1-2).

* Function: Pepsin is a protease, meaning it breaks down proteins. It plays a crucial role in the initial digestion of proteins.

* Adaption: The acidic environment is essential for pepsin's activity. The low pH helps to denature proteins, making them more accessible to pepsin's enzymatic activity.

Let me know if you'd like to learn more about pepsin or other enzymes!