If a toxic enzyme inhibitor causes nonreversible inhibition

If a toxic enzyme inhibitor causes non-reversible inhibition of substrate catalysis then most likely:

A. The target enzyme requires a coenzyme for activity

B. The target enzyme has quaternary structure

C. the target enzyme has more than one binding site

D. the target enzyme has only one binding site

E. none of the above

Solution

The most likely answer is ‘D’. Generally a toxic inhibitor which is a substrate analogue binds at the active site. As it is not the natural substrate, it can’t be modified by the enzyme. It thus blocks the enzyme action. It is an example of non-reversible inhibition.