This is a reaction that students of
biochemistry frequently like a lot
and the reason that they
like this reaction is because
dihydroxyacetone phosphate is becoming converted into the
other product of the previous reaction
When this happens we then have 2
of every molecule that continues
down the pathway of glycolysis.
This way students don't have to learn one
pathway for the dihydroxyacetone phosphate.
and a different pathway for the glyceraldehyde-3-phosphate.
We simply have two glyceraldehyde-3-phosphates to follow.
The enzyme that catalyzes this reaction
is called triose phosphate isomerase
and as an example of what we call
a perfect enzyme. Now in one of the
other lectures that I have given, I have described
what perfect enzymes are. But perfect enzymes
are enzymes that catalyze
reactions amazingly efficiently,
amazingly rapidly with amazingly little material.
The reason of this enzyme does this
here is because there is an intermediate
its in the process of making the
glyceraldehyde-3-phosphate that is extraordinary unstable.
If that intermediate sits around for
any period of time it will fall apart
and this reaction will not occur. So to keep that from happening,
this enzyme has evolved to be very very rapid in its turnover.
So this reaction is also one of these readily
reversible reactions. It doesn't matter
too much to the cell which way it goes and the direction that it
goes is gonna be a function of the concentration of the intermediates.
As you might imagine, this reaction can be
reversed in the process of gluconeogenesis.
So the delta G zero prime is a little positive but
it is not excessive for cell to overcome.
This as I noted is a diffusion limited enzyme and I
will remind you that the diffusion limited enzyme
is one who's rate of reaction
relies only on the rate
with which the substrates can
diffuse into the active site.