Question

Phosphofructokinase is an enzyme that controls the rate of glycolysis. The activity of PFK happens in allosteric regulation by several molecules. Which of the following specific allosteric regulator or regulators would most likely be bound to PFK in yeast cells that are growing in anaerobic conditions?

1. citrate as an allosteric inhibitor

2. ADP as an allosteric inhibitor

3. citrate as an allosteric activator

4. ADP as an allosteric activator

5 AMP as an allosteric activator

6. ATP as an allosteric inhibitor

7 AMP as an allosteric inhibitor

8. ATP as an allosteric activator

Answer 1

Phosphofructokinase (PFK) is one of the most important enzyme that controls the rate of glycolysis in both aerobic and anaerobic respirations. The activity of PFK, being an allosteric enzyme is regulated by many molecules such as citrate, PEP, AMP, ADP, ATP etc which acts as its activators and inhibitors.

PFK catalyzes an important step of glycolysis which is the conversion of fructose-6-phosphate and ATP to fructose-1,6-bisphosphate and ADP. The reactions seems to be as follows:

PFK in yeast cells that are growing under anaerobic conditions is most likely to be bound with some regulators such as citrate as an allosteric inhibitor, AMP as an allosteric activator, ADP as an allosteric activator and ATP as an allosteric inhibitor. The decrease in the ratio of ATP to ADP will increase the catalytic function. Interestingly, ATP acts as substrate and also as a regulator of the enzyme individually.