What characterizes reversible inhibitors?

• A. Bind non-covalently to the enzyme
• B. Bind covalently to enzyme
• C. Bind irreversibly to enzyme
• D. Modify the substrate

Answer: (A)

Reversible inhibitors are defined by their ability to bind to the enzyme through non-covalent interactions—like hydrogen bonds, ionic contacts, and other weak forces—that let the inhibitor detach. Because the binding isn’t permanent, the enzyme can regain activity when the inhibitor concentration falls or the inhibitor dissociates, making the effect controllable and reversible. This is why non-covalent binding best characterizes reversible inhibition. In contrast, covalent binding would permanently modify the enzyme and cause irreversible inhibition, not the reversible kind. Modifying the substrate isn’t how reversible inhibitors are defined, since the action is on the enzyme’s ability to interact with the substrate rather than altering the substrate itself.