When enzymes are outside their optimal pH range, their activity can be disrupted or completely inhibited. Enzymes are sensitive to changes in pH, and deviations from their optimal pH can cause them to denature or lose their shape, which in turn affects their ability to bind to their substrate and catalyze reactions. This can lead to reduced enzyme activity or even complete loss of function. Additionally, extreme pH levels can also cause irreversible damage to the enzyme, rendering it inactive.
