Question

An enzyme may be rendered inoperative by

• A. adding apoenzyme
• B. doubling its concentration
• C. blocking its active site
• D. removing byproducts as soon as they are formed

Answer 1

The correct option is C blocking its active site

An enzyme can be rendered inoperative by blocking its active site. The site at which a substrate binds to an enzyme is called an active site or the substrate-binding site. If these sites are blocked, then the enzyme will not be able to bind to the substrate molecules leading to no production of the product.

If substrate molecules are abundant, doubling the concentration of enzyme will increase the rate of reaction and formation of product(s).
Removing byproducts can also lead to an increase in the rate of reaction by favouring the reaction to proceed in the forward direction. To maintain an equilibrium state, the reaction will occur to form more product(s), if they are removed as soon as they are formed. Conversely, if by-products are added in the reaction mixture, the reaction will slow down, and the rate of formation of new product(s) will be decreased.

If the enzyme is made up of a non-protein part (cofactor) along with the protein part (apoenzyme), the enzyme is known as conjugated enzyme. When cofactor is bound to the apoenzyme, it is known as the holoenzyme. The cofactor is responsible for the catalytic activity and apoenzyme alone doesn’t have biological activity.