Enzymes function best at the normal pH level they were made to be in. Most work best at a neutral pH level (7), but some enzymes such as pepsin (located in the stomach) work best in very acidic pH levels. If the pH level becomes too acidic for the enzyme, it can lead to denaturing of the enzyme's active site.
Enzymes are affected by changes in pH. The most favorable pH value - the point where the enzyme is most active - is known as the optimum pH. Extremely high or low pH values generally result in complete loss of activity for most enzymes.
