Which of the following stimulates phosphofructokinase in the liver?

Question

BlackTom AI · Accepted Answer

To analyze which molecule stimulates phosphofructokinase in the liver, we first recall the key allosteric regulators of PFK-1. PFK-1 is a rate-limiting enzyme in glycolysis and is activated by certain signals that indicate the cell needs to generate ATP, as well as by specific glycolytic intermediates.

Option 1: glucose 6-phosphate. G6P is an intermediate in glycolysis and can reflect glycolytic flux, but it is not a primary allosteric activator of PFK-1. In many contexts, G6P can indicate abundance of upstream substrates, yet it does not directly stimulate PFK-1 activity. This makes this option unlikely as the stimulating molecule.

Option 2: fructose 2,6-bisphosphate. This molecule is a potent allosteric activator of PFK-1, especially in the liver, where it can override high ATP and promote glycolysis by strongly enhancing the enzyme’s activity. This aligns with the well-established regulatory role of F2,6BP in hepatic glycolysis.

Option 3: NAD+. Although NAD+ is a crucial cofactor in glycolysis and many redox reactions, it does not serve as a direct allosteric activator of PFK-1. Its role is more about redox balance than directly increasing PFK-1 activity.

Option 4: ATP. ATP is a classical inhibitor of PFK-1 when energy charge is high; it signals that the cell already has enough energy, so glycolysis slows down. Therefore, ATP does not stimulate, it inhibits, PFK-1.

Option 5: none of the above. Given that fructose 2,6-bisphosphate is indeed a valid stimulator of PFK-1 in the liver, this option is incorrect.

Overall, the reasoning points to fructose 2,6-bisphosphate as the correct stimulator, with each of the other choices either not affecting PFK-1 directly in a stimulatory way or actually acting as an inhibitor or non-regulatory molecule.

Which of the following stimulates phosphofructokinase in the liver? 单项选择题

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