Effect of pH
Each enzyme has an optimum pH. Above or below an enzyme’s optimum pH, its
activity is lower. The optimum pH of a particular enzyme corresponds to the pH of its
natural environment. For many enzymes, this corresponds to pH values of around 7. For
pepsin, which is active in the stomach, the optimum pH is 2 (the pH of the stomach).
Trypsin, which is active in the small intestine, has an optimum pH of 8 that matches the
pH of the small intestine.