Examples of F26P and flux in other tissues

Question 1

Why do tissues control systems differ from the liver and how?

Answer 1

WHy: do not want these organs doing the same thing

Question 1

skeletal muscle

Answer 1

no glucagon receptor present.
If glucagon released in response to blood sugar, muscle does not care.
Isozyme also has no Pi sites, therefore there is no cAMP control in the skeletal muscle.
If fight or flight, your muscles will notice vast amount of glucose in the blood and pull it in.

Availability control is done by F6P:
- increase F6P increases PFK2 activity which increases F26P which increases PFK1 which increases Glycolysis!!

Question 2

Heart

Answer 2

Two. separate serines (ser 466 and ser 483)

Phosphorylation will activate PFK2 while dephosphorylation will activate FBPase-2 (exactly opposite of the liver)

This means heart can switch fuel sources. Under resting conditions, heart will use fatty acids. If fight/flight kicks in, body will use glucose quickly for heart, but eventually will use fatty acids again

The heart has a small glycogen store for heavy workloads; but usually fatty acids end up being used (and blood glucose as well)

(AMPK will affect ser 466, also PKA will affect ser 466 and ser 483)