Question

Name one enzyme of glycolysis that catalyzes an essentially irreversible step: __________

Answer 1

Answer:

Phosphofructokinase-1

Explanation:

Phosphofructokinase-1 catalyzes the phosphorylation of fructose 6-phosphate into fructose 1,6-bisphosphate. The reaction is exergonic with a large negative free energy change to make it essentially irreversible.  

Phosphofructokinase-1 is an allosteric enzyme with regulatory sites. Higher ATP concentration serves to inhibit the phosphofructokinase-1 by binding to the allosteric site of the enzyme and thereby reducing its affinity for the substrate (fructose 6 phosphate).