Effect of pH on Rate of Reaction

Enzymes are pH sensitive. As a result they will have an optimal level, and changes from that optimal level will result in decreased performance. The optimum pH usually occurs at about 7 (neutral). If the optimum pH of an enzyme is about 2-3 (e.g. pepsin), then the peak would be skewed to the left resulting in a peak performance at about 1-2 and a rapid fall off thereafter.

The graph above shows the activity of pepsin in comparison to that of trypsin – an enzyme that works best in an alkaline environment.