Question

The enzyme hexokinase which catalyses glucose to glucose-6-phosphate in glycolysis is inhibited by glucose-6-phosphate. This is an example of

• A. Competitive inhibition
• B. Non-competitive inhibition
• C. Feedback allosteric inhibition
• D. Positive feedback

Answer 1

The correct option is C Feedback allosteric inhibition

Allosteric inhibition is reversible non-competitive inhibition occurring in case of allosteric enzymes. Herein, the inhibitors are the products or intermediates of reactions catalysed by the enzymes. With too much of this product produced, the final product binds to an allosteric site on the first enzyme in the series of reactions to inhibit its activity. Hence, it is also called end product inhibition or feedback inhibition.
Hexokinase catalyses glucose to glucose-6-phosphate in glycolysis and is inhibited by the product. This is called feedback allosteric inhibition.
Competitive inhibition is the reversible inhibition of enzyme activity due to presence of substrate analogues.
Non-competitive inhibition is the reduction of enzyme activity by a factor that has no real structural similarity with the substrate.