Regulation : Glycogen Catabolism Flashcards
What is a normal blood glucose range?
3.6 - 5.8 mM (fasting glucose)
What are the two names for glucose levels out of range?
Hyperglycemia
Hypoglycemia
Which enzymes are regulated in glycogen catabolism?
Glycogen phosphorylase
- reactions are irreversible
What enzymes are regulated in glycolysis?
Hexokinase (1)
PFK-1 (3)
Pyruvate kinase (10)
- all are irreversible.
What type of enzyme is glycogen phosphorylase?
Why is it like this?
- shape shifting in the dimer ( to turn on GP)
= phosphorylation on Serine 14 creates more active form sometimes called phosphorylase a(active)
phosphorylase b(less-active unphosphorylated form)
By binding of AMP in muscle cells.
What is the binding of AMP in muscle cells to glycogen phosphorylase an indicator of?
Low energy indicator
How is phosphorylation of glycogen regulated?
By hormones glucagon and adrenaline.
What is released when blood glucose is low?
Both glucagon (liver) and adrenaline (muscle cells)
What do glucagon and adrenaline bind to in order to activate?
By activating a signalling (receptors_ cascade - activates Protein Kinase A (PKA)
What is the resulting reaction of PKA being activated?
Phosphorylation and activation of glycogen phosphorylase this causes glycogen breakdown -> glucose 1- phosphate production.
What is the result of phosphorylation of glycogen phosphorylase?
Glycogen catabolism in myocytes and hepatocytes.
How is glycogen phosphorylase turned off? AMP is high - glucose high
Glucose binds on to allosteric sites - phosphate group changes position - hangs out, exposed = dephosphorylated (phosphatase)
Glycogen phosphorylase and glycogen synthase are ?
Reciprocally regulated - GP is on GS is off and vise versa.
What is a major activator of Glycogen synthase?
Insulin = active non-phosphorylated form.
Insulin turns off glycogen phosphorylase.
Turns on Glycogen synthase.
