In glycolysis, which enzyme catalyses the rate-limiting phosphorylation of fructose-6-phosphate?

Correct option is D

The correct answer is: (d) Phosphofructokinase-1 (PFK-1)

Explanation:

• Phosphofructokinase-1 (PFK-1) is the key regulatory (rate-limiting) enzyme of glycolysis.

• It catalyzes the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate using ATP.

• This step is irreversible and is highly regulated by cellular energy levels (ATP/AMP ratio), making it the commitment step of glycolysis.

Information Booster:

• PFK-1 is allosterically inhibited by ATP and activated by AMP and fructose-2,6-bisphosphate.

• This step is considered the first committed step in glycolysis.

• Glycolysis occurs in the cytoplasm of cells.

• Total ATP yield from glycolysis is 2 net ATP molecules per glucose.

• Glycolysis is anaerobic, i.e., does not require oxygen.

• PFK-1 is crucial in controlling glucose metabolism and energy production.

Additional Information:

• Pyruvate kinase – Catalyzes the final step of glycolysis: phosphoenolpyruvate (PEP) to pyruvate.

• Glyceraldehyde-3-phosphate dehydrogenase – Converts G3P to 1,3-bisphosphoglycerate; involved in energy-yielding steps but not rate-limiting.

• Hexokinase – Catalyzes the first step: glucose to glucose-6-phosphate; important but not the main rate-limiting step.