Question

Select the option which is not correct with respect to enzyme action.

• A. Substrate binds with enzyme at its active site.
• B. Addition of lot of succinate does not reverse the inhibition of succinic dehydrogenase by malonate.
• C. A non-competitive inhibitor binds the enzyme at a site distinct from that which binds the substrate.
• D. Malonate is a competitive inhibitor of succinic dehydrogenase.

Answer 1

Answer: (B)

The reduction of activity of succinate dehydrogenase by malonate is an example of competitive inhibition. Competitive inhibition is a reversible inhibition where inhibitor competes with the normal substrate for the active site of enzyme. A competitive inhibitor is usually similar to the normal substrate and, therefore, fits into the active site of an enzyme and binds with it. The enzyme, now cannot act upon the substrate and reaction products are not formed. Hence, action of an enzyme may be reduced or inhibited. Since a competitive inhibitor occupies the site only temporarily, the enzyme action is not permanently affected. Thus, addition of a lot of succinate can reverse the inhibition of succinic dehydrogenase by malonate.