Lec B Flashcards
How will insulin regulate the bifunctional enzyme PFK-2/FBPase?
Insulin will dephosphorylate phospho-protein phosphatase and then dephosphorylate the PFK-2 domain of the bifunctional enzyme turning on it’s activity which will PFK1 to phopshorylate F6P to F26B.
Sustained glucagon signaling at the liver cells will lead to increased levels of genetic expression of what ? Gluconeogenic enzymes.
Gluconegentic enzymes - in particuar pep CK. Sustained glucagon signalling will lead to increased transcripitional expression and translational expression of enymzes of GNG and anytime you raise reversible enzymes in a pathway you increase flux through the pathway. That is a slower response than phopshorylation, covalent modification, and allosteric modification. This takes anywhere from hours to days.
What does glycogen phosphoylase do?
Eats away at the alpha 1-4non reducing end of glycogen granula and breaks off a glucose1 phopshpate.
True of False:
Glycogen phosphorylase a and phosphorylase b are both active forms of the enymze.
True:
Glycogen phosphoylase b is just less active than phosphorylase a. Why? because (b) has a phosphate making it a little more active and (a) has a OH group (still active) but just less active.
How is glycogen phoshprylase regulated?
It can be covalently modified and allosterically modified as well. In the liver Glucose and G6P inhibit the enzyme allosterically.
Phosphorylase kinase does what?
Phosphorylates Glycogen phosphorylase converting it to (a) and this makes it more active.
What are the different ways that PKA can be activated in different tissues? Specifically through epinephrine or glucagon.
PFK2/FBPase2 in the liver it phosphorylates and inactivates the kinase (PFK2) domain whereas in the cardiac tissue it is the phosphatase domain that gets phosphorylated and inactivated by PKA.
In the liver under low blood sugar circumstances, from the catalytic subunit being released from PKA (by cAMP) what also happens in the liver besides regulating the bifunctional enzyme?
PKA will also phosphorylase phosphorylase kinase will activate glycogen phosphorylase which will break down glycogen.
How does epinephrine affect regulation in the Liver?
When epiniphrine is released in flight or fight response, the liver cells have an receptor that can be bound by epinehprine which will release Ca from the ER which will fully activate the phosphorylase kinase.
