The first glycolysis rate-limiting enzyme is under various allosteric regulations. This protein is nearly inactive because of inhibition by ( ) under physiological conditions. The activity is restored by ( ), its most potent allosteric activator. a. AMP citrate
b. AMP Fru-2,6-P2
c. ATP citrate
d. ATP Fru-2,6-P2
e. All of these

d. ATP;  Fructose-2,6-bisphosphate

Explanation:

Phosphofructokinase-1 is the enzyme that catalyzes the formation of fructose-1,6-bisphosphate from fructose-6-phosphate and ATP. The phosphofructokinase step is the first rate-limiting step of glycolysis.

Phosphofructokinase-1 activity is allosterically regulated. Its activity is increased whenever the cell's ATP supply is depleted or when its breakdown products, ADP and AMP accuulates in he cell. However, it is inhibited when the cell is amply supplied with ATP.

The activity of phosphofructokinase-1 is restored by fructose-2,6-bisphosphate, its most potent activator.

From the given options:

a. AMP citrate  is wrong because AMP increases the activity of phosphofructokinase-1 and citrate is not its activator but an inhibitor

b. AMP Fru-2,6-P2  is wrong because AMP increases its activity same as fructose-2,6-bisphosphate

c. ATP citrate  is wrong because both citrate and ATP are inhibitors

d. ATP Fru-2,6-P2  is correct as explained above

e. All of these is wrong because of the other wrong options above.

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