Question

In glycolysis, the rate limiting enzyme is

• A. Glucokinase
• B. Phosphofructokinase
• C. Phosphohexose isomerase
• D. Aldolase

Answer 1

The correct option is B Phosphofructokinase

The rate-limiting step in glycolysis is the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate, which is catalysed by the enzyme phosphofructokinase. So, phosphofructokinase is called as rate-limiting enzyme in glycolysis. It is an energetically favourable step, irreversible and a different pathway must be used to do the reverse conversion during gluconeogenesis. This makes the reaction a key regulatory point. Thus, option B is correct.
Glucokinase or hexo kinase involved in the conversion of glucose to glucose-6-phosphate. This step is not the rate-limiting step in glycolysis.
Phospho hexoisomerase catalyses the conversion of glucose-6-phosphate to fructose-6-phosphate. This step is not the rate-limiting step in glycolysis. Aldolase catalyses the conversion of fructose-1.6-bisphosphate to dihydroxyacetone phosphate. This step is not the rate-limiting step in glycolysis.

So, the correct answer is option B.