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).

DGo'

+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.

Keq

Comments

 This enzyme proceeds through a mandatory phospho-enzyme intermediate (phsophate is covalently linked to an amino acid side chain of the enyzme). The phospho-enzyme intermendiate then transfers the phosphate back to glycerate.

"In cell" Substrate Concentrations*

 

 

S1 =

3-Phosphoglycerate

0.12 mM

S2 =



P1 =

 2-Phosphoglycerate

0.03 mM

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

Glycerate Mutase. Animation of the Glycerate Mutase reaction Blue: represents the enzyme. "Start" begins an animation of the group transfer reaction. It proceeds through the reaction in the "forward" direction and then "backwards" again. Note how the enzyme is involved. "+" increases speed while "-" decreases the animation speed. You may also step through the reaction using "next" or "previous"

The metal ion initiate the process by altering the ionization of the active site Serine. It can then attack the phosphate on C3 of glycerate - making the phosphoenzyme intermediate. The metal ion can alter the ionization od the C2 alcohol so that it can attack the phosphopenzyme intermediate - generating the final product.

Compare the animated reaction to the "arrow pushing" scheme at the right. See if you can correlate the electron movement in the animation to the arrows in the static picture above.

Picture of Enzyme with substrate


  1. Ribbons Glycerate Mutase protein backbone shown in ribbons
  2. With substrate 2-P-Glycerate is added in the atom colored spheres. C=Gray; O=red; N-blue; P=Orange. The Phosphate is on C2 and is at the bottom left of the substrate in this picture, The C1 carboxyl group is pointing out of the picture at you
  3. Mn ions added Same picture as in "2" but with the two Mn ions added in. One is i contact with the phosphate. The catalytic Mn is not, nut appears to be just left of the substrate.
  4. Active Site Amino Acid Sidechains As in "3" but with the Actice Site Amino Acid Sidechains added. Notice all the ARG and NIS and LYS near the phsophate and the carboxyl group.
  5. Ribbons removed and closeip As in "4" but a closeup of the actieve site and the ribbons removed
  6. ACtive site Ser phosphorous atom AND C3 of 2-P glycerate in cyan The catalytic SER is in cyan. notice its proximity to an Mn ion AND the phosphate gropu on C2. C3 is also highlighted it appears to be pointing away from the where the SER is in this picture.
Click on an atom to diplay identity here
Messages about the currently highlighted features