Why are enzymes active at a narrow ph value?

An enzyme is a protein and therefore has a large number of open amino acid side chains with a charge that depends on its pH and the pH of the solution in which it occurs. This amino acid composition also denotes a specific form of protein folding of the enzyme and exhibits its catalytic zone. Any change in pH, a change in the side chains of ion dependence and, therefore, leads to the coagulation of the enzyme protein.

Binding to another protein can alter the expression of these charged residues and alter the folding of the enzyme protein through protein-protein interactions.