This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzymes, Subject name: Biochemistry
PKF-I Inhibitor 
Select and explain. 
A. AMP, B. Citrate, C. Glucose 6 phosphate, D. Insulin
B: Citrate
Answer: B: Citrate 
Explanation: Phosphofructokinase (PFK) (step 3) of glycolysis is the most impoant rate-limiting enzyme for glycolysis pathway. ATP and citrate are the most impoant allosteric inhibitors. AMP acts as an allosteric activatorRef: DM Vasudevan, Page no: 98