Which Enzymes' Catalytic Activity Is Predicted to Be Most Sensitive

Which enzymes' catalytic activity is predicted to be most sensitive to changes in pH?

A) Enzymes with nonpolar side chains at the active site
B) Enzymes with amino (-NH₂) or carboxy (-COOH) side chains at the active site
C) Enzymes with metal ions bound to nonpolar side chains at the active site
D) Enzymes with structurally smaller side chains (e.g., -H) at the active site
E) Enzymes with structurally rigid side chains (e.g., proline residues) at the active site