Question

Where does inhibitor bind on enzyme in mixed inhibition?

• A. At active site
• B. Allosteric site
• C. Enzyme – substrate complex
• D. Binds on substrate

Answer 1

The Correct Option is B

Mixed inhibition is a specific form of enzyme inhibition in which the inhibitor binds not only to the free enzyme but also to the enzyme-substrate complex, typically at an allosteric site. 

Step 1: Understanding Mixed Inhibition - In contrast to competitive inhibition, mixed inhibitors do not bind directly to the active site of the enzyme. - Instead, they bind to an allosteric site, which is a site distinct from the active site, altering the enzyme's conformation. - This changes both the enzyme's affinity for the substrate and its catalytic activity. 

Step 2: Evaluating the Options - Option (A) - Incorrect: In mixed inhibition, the inhibitor does not bind to the active site; instead, it binds elsewhere on the enzyme. - Option (B) - Correct: The inhibitor in mixed inhibition binds to an allosteric site, affecting enzyme function and substrate interaction. - Option (C) - Incorrect: While the inhibitor can affect the enzyme-substrate complex, its primary binding site is at the allosteric site. - Option (D) - Incorrect: The inhibitor does not bind directly to the substrate in mixed inhibition. 

Step 3: Conclusion Since mixed inhibition involves binding at an allosteric site, option (B) is the correct answer.