So in summary what we have seen over the past
couple of pathways are as follows.
Epinephrine, glucagon binding stimulates the
phosphorylation of all glycogen enzymes.
The phosphorylation of the glycogen
breakdown enzymes like glycogen phosphorylase
will activated favoring glycogen breakdown.
Phosphorylation of the glycogen synthesis
enzyme, glycogen synthase, inactivates it.
Epinephrine also activates glycogen
breakdown and glucose production.
Now if you think about that, that makes sense
if the AM is putting glucose out.
Glucose production comes from gluconeogenesis
and glycogen breakdown produces glucose so that
it can be exported from cells.
These two events are coordinated so that the
body has the glucose that it needs.
Epinephrine inactivates glycogen
synthesis and that makes sense;
because the glucose that you are producing,
you don't wanna waste in a futile cycle.
On the opposite site, insulin stimulates
phosphoprotein phosphatase. So when
insulin is present, blood glucose is
high and the body is wanting to deal with it.
This stimulates the removal of phosphates from
all the proteins that we have talked about before.
That's going to reverse all of those effects.
Glycogen breakdown enzymes become
less active meaning that they are
not breaking down glycogen anymore.
And the glycogen synthase becomes active so it's gonna
grab that glucose that's coming in and deal with it.
So cells start making glycogen
instead of breaking it down.
And cells will also start breaking it down in
glycolysis instead of making it in gluconeogenesis.
So epinephrine and glucagon are stimulated
in the production of glucose.
Whereas insulin is stimulating the use of that
glucose in the synthesis of glycogen.