Denaturation of the enzymes generally refers to conformational changes in protein structure & active site of the enzyme and also results in the inactivity of enzymes.
Enzymes usually require an optimumtemperature and pH for their action.
The temperature or the pH at which the compound shows its maximum activity is called the optimum temperature or optimum pH, respectively.
A temperature or pH more than optimum may alter the molecular structure of enzymes.
Generally, an optimum pH for enzymes is considered to be ranging between 5 & 7.