Question:medium
Which element is required by phosphofructokinase?
Which element is required by phosphofructokinase?
Show Hint
Kinases use ATP as the Mg-ATP complex - which metal?
Updated On: Jun 24, 2026
- Magnesium
- Inorganic phosphate
- Manganese
- Copper
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: Place PFK-1 as the committed, rate-controlling enzyme of glycolysis that phosphorylates fructose-6-phosphate using ATP.
Step 2: Every ATP-dependent kinase needs a divalent metal, and for PFK that metal is magnesium. ATP actually binds the active site as Mg-ATP, where the $Mg^{2+}$ shields the repulsive negative charges of the phosphate chain and aligns the gamma-phosphate for transfer.
Step 3: Crystal structures place a magnesium ion bridging the phosphoryl groups of ADP and fructose-1,6-bisphosphate in the catalytically closed conformation, so its presence is essential for turnover.
Step 4: Inorganic phosphate is not the cofactor here, and neither manganese nor copper serves as the natural metal for this enzyme. The required element is magnesium.
\[\boxed{\text{Magnesium}}\]
Step 2: Every ATP-dependent kinase needs a divalent metal, and for PFK that metal is magnesium. ATP actually binds the active site as Mg-ATP, where the $Mg^{2+}$ shields the repulsive negative charges of the phosphate chain and aligns the gamma-phosphate for transfer.
Step 3: Crystal structures place a magnesium ion bridging the phosphoryl groups of ADP and fructose-1,6-bisphosphate in the catalytically closed conformation, so its presence is essential for turnover.
Step 4: Inorganic phosphate is not the cofactor here, and neither manganese nor copper serves as the natural metal for this enzyme. The required element is magnesium.
\[\boxed{\text{Magnesium}}\]
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