As we saw, in amino
glutamic acid or glutamate is central
to the balancing of the amines
and the ammonium ions that are produce
during amino acid metabolism.
And we're going to see how that happens
in the body as well with this slide.
Now this is a complicated slide, so
I'm going to step you through it
sequentially and fairly carefully to
make sure all the points are made.
First of all, glutamic
acid can be converted to
glutamine by the enzyme
That reaction is important from a
nitrogen balance perspective because
ammonium ions are produced as a
byproduct of amino acid metabolism.
They have to be
sopped up as it were.
And they're sopped up
partly by this reaction.
Glutamine could be converted back to
glumatic acid, but you'll notice this
is not the exact reverse of the
reaction that produced the glutamine.
Instead the amine that was put on to
glutamine, the ammonium that was put
on to glutamine to make the amine
is converted back onto an alanine.
So that what is happened in the process of
going up and the then down in this reaction
is the ammonium ion on the
left has been converted
into an amine that is
carried on an alanine.
Ammonium ion is toxic.
The amine on alanine is not.
Now alanine as we will see plays
into the glucose alanine cycle.
Glutamic acid can also be converted
as we have seen in the
amino acid metabolism
and the byproduct to that reaction
is the release of an ammonium ion.
Now there are places in the body
where we want to sop up ammonium
that place in the
body being the brain.
And there are places in
the body where we want
to release ammonium so
that we can make urea.
That happens in the kidney
and also in the liver.
We see that alpha-ketoglutarate
can also soak up
ammonium ions and produce
glutamic acid as we see here.
This gives the cell and the body an additional
way of handling those ammonium ions.
We also see that
alpha-ketoglutarate can become
glutamic acid by a
In this case, alanine is
donating its amine to
become glutamic acid.
So now we see a lot of possibilities
and a lot of different directions
that we can go in order to make or
break down these individual molecules.
Last, we see glutamic acid that can
go back to alpha-ketoglutarate
by the reversal of the transamination
reaction that I've just described to you.
Now alanine is outputted to
the glucose alanine cycle.
This, as I described
earlier, is an important
consideration for brain
and other tissues that
want to lose the amine
but don't want to lose
the glumatic acid that's
important to them.
The glucose alanine cycle can feed
its alanine into another process.
So we see in this case that the
alanine that moved into the cycle
transfers to another part of the
body where that alanine is donated,
the amine on the alanine is donated
in another way to get rid of it.
So if we look at this
overall process happening
in the body, what I like
to do is sort of follow
what happens with these
ammonium ions that start
on the left and where
they ultimately end up.
So we can imagine we've got
catabolic processes involving
amino acids as we discussed
in amino acid catabolism.
That produces ammonium ions that
are shown by the arrows above.
Those ammonium ions can
be gobbled either by the
alpha-ketoglutaric acid or by the
glutamic acid to make glutamine.
Both of those
processes can occur.
So let's follow.
If we follow here
the dark arrows,
we see first gobbling up of the
ammonium ions form alpha-ketoglutarate.
They also gobbled up by the glutamic
acid going to make glutamine.
Glutamine transfers that nitrogen
as we've discussed to an alanine.
That alanine goes to the glucose-alanine
cycle in one direction.
Or the glutamic acid that's
the product to that can
transfer its amine to alanine
in a separate reaction.
In either case, those
alanines make it to the
via the bloodstream.
In the bloodstream, the
alanine moves to another
part of the body where
that alanine is then
donated -- I'm sorry,
with the amine is donated
to remake glutamic acid.
The glutamic acid then
dumps its ammonium ion
and in dumping its ammonium
ion, urea is made.
Now this scheme that I've shown
you is actually what happens
with the movement of all
the materials in the body.
Urea is excreted in the urine.
That gets rid of that toxic
substance that we started with.
If we look now and we say that the
bottom part that's colored in yellow
occurs in the liver or kidney which
is of course where it does occur.
The rest of the body has a
way of handling all of that
toxic ammonium ion and getting
rid of it as we see here.