One important enzyme in glycolysis m mammals is phosophofructokinase-1 (PFK-1).

Question

One important enzyme in glycolysis m mammals is phosophofructokinase-1 (PFK-1). Show the reaction that is called by this enzyme. The two graphs below show The rate of PFK-1 activity versus fructose 6-phosophate (F6P) in the presence of 0.01 mM ATP, 2 mM ATP, and 2 mM ATP only The rate of PFK-1 activity in the presence or absence of fructose-2, 6-bis phosphate (F26BP). Graph a). Which line is "normal"? Explain the effects on the reaction rate of the different concentrations of ATP with or without AMP. Are ATP and AMP substrates or regulators or both? Why the differences between the curves? How do these adenylate compounds (ADP and ATP) help regulate the rate of the whole glycolysis pathway? Graph b) Based on the second graph, what is the effect of F2.6BP on PFK-1 activity? How does F2.6BP change the enzyme's K_M?

Explanation / Answer

2). Glycolysis is an anaerobic process, through which one glucose molecules is breakdown into two molecules of three carbon pyruvate. The glycolysis of each glucose molecule generates 2 ATP molecules.

The flow of electrons and the flow of phosphorus atoms: In the first step, the glucose is phosphorylated by the enzyme hexokinase. One phosphate molecule from ATP is transferred into glucose resulting in the prodution og glucose-6-phosphate and ADP.

Glucose+ hexokinase + ATP -----------> Glucose-6-phosphate + ADP

2) Glucose-6-phosphate now isomerises to fructose-6-phosphate by the enzyme phosphoglucoisomerase.

3) Fructose-6-phosphate again undergoes phosphorylation process in the presence of phosphofructokinase by gaining a phosphate group from the ATP, resulting in the production of fructose-1,6-bisphosphate.

Fructose-6-phosphate + ATP + phosphofructokinase --------------------> fructose-1,6-bisphosphate + ADP

4) Fructose-1,6-bisphosphate now undergoes a destabilization reation in the presence of aldolase enzyme giving rise to the production of two isomers namely dihydroxyacetone phosphate and glyceraldehyde phosphate.

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