The idea in this group transfer reaction is to have the -OH group on the C1 alcohol carbon of fructose to "attack" the terminal phosphate of ATP.

-OH is not a good attacking agent for a group transfer reaction- it would be much better if it were unprotonated -O- instead.

  1. Both substrates (Fructose-6-P and ATP) must be in the active site at the same time.
  2. The first step in the catalysis after both substrates have bound to the active site involves "base catalysis". An amino acid side chain (Asparate in the case of phosphofructokinase-1) helps to remove a proton from the -OH to generate the required -O- and the protonated Aspartic Acid.
  3. The -O- attacks the terminal phosphate.
  4. This causes "too many bonds" to phosphate so one pair of electrons must exit - these end up as a minus charge on what used to be the "middle" phosphate of ATP.

The results of the previous steps are shown.

  1. The Aspartic Acid is protonated,
  2. what used to be the terminal phosphate is now bonded to C1
  3. What used to be the middle phosphate is now the terminal phosphate on ADP. Note; this phosphate had only one negative charge on it when it was part of ATP; it now has two negative charges.

Not shown: as the pH of the surrounding solution is higher than the pK for Aspartic Acid, the proton will likely dissociate and thus regenerate the base for of Aspartate again so that the enzyme can continue to function.

Anaerobic Glucose Metabolism

Phosphofructokinase Information

Enzyme Name

Phosphofructokinase (PFK-1)

Reaction Catalyzed

ATP Dependent Phosphorylation of C1 of Fructose-6-Phosphate

Reaction Type

Group Transfer

Pathway Involvement

Glycolysis ONLY

PhosphoFructokinase (PFK-1) is not part of the gluconeogenesis pathway. In gluconeogenesis a separate enzyme (Fructose-1,6-bisphosphatase) hydrolyzes a phosphate from C1 Fructose-1,6-bisphosphate and is not ATP dependent. Rather it performs a simple hydrolysis reaction to cleave off phosphate.


ATP is a cosubstrate;ADP is a coproduct

cosubstrate/coproduct = molecules that enter and leave the active site along with the substrate/product and are generally altered in the reaction as well

cofactors = nonprotein molecules that are required for a reaction that are generally a permanent part of the enzyme. These remain unaltered after the reaction is complete.