The idea in an isomerization reaction is to have a combined acid and base catalysis in a "push-me pull-you" setup.

  1. There is a base adjacent to the proton on C2 and an acid near by the C=O group on C1.
  2. The base pulls on the proton of C2 (This looks as if it makes a C- on C2) at the same time that one pair of electrons "moves up" from the C=O toward the acid group (generating a too few bonds to C1)
  3. The "extra" charge on C2 moves moves to fill the void on C1 as the pair of electrons moves away from the C=O.

The results of the previous steps are shown.

  1. The sidechain that acted as a base in now protonated
  2. THe sidechain that was an acid is now unprotonated and its proton resides on the oxygen attached to C1
  3. There is an apparent carbon-carbon double bond. This arrangement between C1 and C2 is called an Ene-diol and is extremely unstable - and in fact lasts an extremely short period of time

The sequence can go exactly reverse and generate the starting material or go forward

  1. The sidechain that WAS an acid is now a base. it attracts the proton from the -OH on C2
  2. The negative charge that results on the -O- swings down toward the C2 carbon while one of the bonds in the C=C moves out to capture the proton on the nearby acid.

The results of the previous steps are shown.

  1. The amino acid sidechains are back to their original protonation states
  2. The relative position of the aldehyde and alcohol have swapped

From this position try to see how the reaction would go in reverse. Remember the ΔGo' and the ΔG are small - this reaction is easily reversible.

Anaerobic Glucose Metabolism

Phosphoglucose Isomerase Information

Enzyme Name

Phosphoglucose Isomerase

Reaction Catalyzed

Isomerization of Glucose-6-P to Fructose-6-P

Reaction Type

Isomerization

Pathway Involvement

Both Glycolysis and Gluconeogenesis

This reaction is freely reversible and in fact the STANDARD Free Energy of this reaction favors gluconeogenesis by a little bit. The observed reaction direction can easily be influenced by the substrate and product ratio (ΔG for these conditions - check out the thermodynamics tab)

Cofactors/Cosubstrates

None