Question

Inhibition of Succinic dehydrogonase enzyme by malonate is a classical example of:

• A. Cofactor inhibition
• B. Feedback inhibition
• C. Competitive inhibition
• D. Enzyme activation

Answer 1

The Correct Option is C

Step 1: Understanding Enzyme Inhibition:

Enzyme inhibition occurs when a substance (inhibitor) binds to an enzyme, reducing its activity. Inhibition can be competitive, non-competitive, or uncompetitive depending on how the inhibitor interacts with the enzyme.

Step 2: Competitive Inhibition:

In competitive inhibition, the inhibitor molecule resembles the substrate and competes for the same active site on the enzyme. This prevents the substrate from binding to the enzyme and reduces the enzyme's activity. However, if the concentration of the substrate is high enough, it can overcome the effect of the inhibitor by outcompeting it for binding to the enzyme.

Step 3: Analyzing the Given Options:

Option 1: Non-competitive inhibition

In non-competitive inhibition, the inhibitor binds to a site other than the active site, changing the enzyme's shape and making it less effective. This does not apply in the case of malonate and succinic dehydrogenase.

Option 2: Uncompetitive inhibition

Uncompetitive inhibition occurs when the inhibitor binds only to the enzyme-substrate complex, preventing the reaction from proceeding. This is not the case with malonate.

Option 3: Competitive inhibition

In this case, malonate competes with the substrate (succinate) for the active site of the enzyme succinic dehydrogenase. Malonate resembles the substrate closely and directly competes with it for binding, which is a clear example of competitive inhibition.

Option 4: Allosteric inhibition

Allosteric inhibition involves the inhibitor binding to a site other than the active site (an allosteric site), causing a conformational change that affects the enzyme’s activity. This is not relevant to malonate and succinic dehydrogenase.

Step 4: Conclusion:

The correct type of inhibition in this case is competitive inhibition, where malonate competes with succinate for the active site of the enzyme.

Answer: The correct answer is Option 3: Competitive inhibition.