Multiple choice

The rate limiting step of glycolysis is controlled by

  1. Pfk - I

  2. Pfk - II

  3. Glyceraldehyde-3-phosphate dehydrogenase

  4. Hexokinase

  5. Aldolase
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A Correct answer
Explanation

Physiological concentration of ATP in cell inhibits Pfk-I allosterically and reduces its substrate affinity for fructose 6 phosphate. A 20% fall in ATP concentration rises the the rate of glycolysis 10-fold and Pfk activity to 50%. So low ATP/AMP ratio regulates the Pfk-I activity and thus, regulates glycolysis. Thus, Pfk-I is the enzyme for rate limiting step of glycolysis.

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