Glycerate Mutase Information

Enzyme Name

Glycerate Mutase

Reaction Catalyzed

Group Transfer of phosphate from C₃ to C₂ of glycerate

Reaction Type

Group Transfer Reaction

Rationale

 This is a group transfer reaction. This is most easy to visualize when you look at the mechanism of the reaction (see below). The phosphate is transferred from one alcohol to another through a phopshoenzyme intermediate. In effect there are two group transfer reaction... 1. transfer of phosphate to the enzyme and 2. transfer of phosphate from the enzyme back to glycerate.
   
Why this is NOT an isomerization reaction.... Note that 3-P glycerate and 2-P glycerate are in fact isomers (they share a common chemical composition but one bond is different). Just because they are isomers does not makde this an isomerization reaction. To the enzyme mechanism an isomerization is a a "swapping" of an adjacent alcohol and aldehyde carbons.

Why is Phosphate moved from C₃ to C₂ - what good is it? This is justified by the next two reactions. Recall what I said about glycerate kinase - that we can transfer a PO₄ to ADP by group transfer if the Standard Free Energy favors it (or is at least close). Right now we are trying to build to one those compounds that has a very high Standard Free Energy of hydolysis for the phosphate group. That high favorable Free Energy will be used to geneate another pair of ATP.

Pathway Involvement

Glycolysis AND gluconeogenesis

Cofactors/Cosubstrates

Many required an active site metal ion to alter the ionization of the important alcohol groups (see mechanism below).

DG^o'

+4.4 kJ/M

Starting from standard state and allowing the reaction to come to equilibrium the 3-phosphoglycerate concentration would end up ~6 times higher than that of 2-phosphoglycerate.

The Standard Free Energy favors Fructose-1,6-bisphosphate production.

K_eq

Comments

"In cell" Substrate Concentrations^*

S₁ =

S₂ =

P₁ =

P₂ =

DG for these conditions

+0.9 kJ/M ... thus under cellular conditions the reaction favors foramtion of 3 phosphoglycerate by a little bit

Mechanism for Chemistry

Mechanism for Enzyme

Picture of Enzyme with substrate

1. RibbonsAldolase. Here only the main chain is represented by these ribbons. There are four identical subunit
2. one subunit with substrate Three of the subunit deleted and a substrate analog (mannitol-1,6-bisphosphate) is added in the atom colored spheres. C=Gray; O=red; P=Orange. three critical AA in the active site are also added.
3. as above closeupSame picture as in "2" but zoomed in
4. substrate rotationas in "3" ribbons deleted and allowed to rotate to show the orientaion of these 3 amino acids. A.) LYS near C2 - this will form the Schiff's base; B.) GLU near C2 - will help the Schiff's base form by "attracting the water" as the Schiff's base forms; C.) LYS near C4 - will help the hydroxyl group deprotonate as the aldol reaction begins.
5. substrate and all nearby AAAll amino acid sidechains near the mannital are turn on
6. Schiff's base LYS in cyan and near GLU in yellow The LYS that will form the Schiff's base is color cyan, C2 of mannitol is colored magenta and the GLU is color yellow. The roles are highlighted in "4"
7. LYS near and near C_{4/sub> in cyan The LYS near C4 is colored cyan, C4 of mannitol is color magenta.}