This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of carbohydrate, Subject name: Biochemistry
The rate-limiting step in glycolysis is catalyzed by 
Select and explain. 
A. Pyruvate kinase, B. Enolase, C. Glucokinase, D. Phosphofructokinase
D: Phosphofructokinase
Answer: D: Phosphofructokinase 
Explanation: Step 3 of Glycolysis Fructose-6-phosphate is fuher phosphorylated to fructose1,6-bisphosphate. The enzyme is phosphofructokinase. ii.PFK is an allosteric, inducible, regulatory enzyme. It is an impoant key enzyme of this pathway. This is again an activation process, the energy being derived by hydrolysis of yet another molecule of ATP. ). This irreversible step is the rate-limiting reaction in glycolysis. However, during gluconeogenesis, this step is circumvented by fructose-1,6-bisphosphatase.Ref: DM Vasudevan, 7th edition, page no: 109