Protein control: (leyland) Carb metabolism 2 Flashcards
Describe regulation of PFK-1 via F26BP
F26BP acts as an allosteric regulator
-> stabilises R state and activates PFK-1
What is PFK-2 and what does it do?
Phosphofructokinase-2 also known as fructose bisphosphatase-2 -> bifunctional enzyme
- Controls intracellular conc. of F26BP in the liver
How is PFK-2 hormonally regulated in the liver?
2 domains (kinase/phosphatase) are not active at the same time -> hormonally regulated via phosphorylation/dephosphorylation
Glucagon stimulates PKA production -> PKA phosphorylates PFK-2 and activates phosphatase domain (+++ gluconeogenesis, — F26BP)
Insulin stimulates phospho-protein phosphatase -> removes phosphate group and activates kinase domain](+++ glycolysis, +++ F26BP)
Mechanisms of phosphofructokinase regulation?
Allosteric regulation by multiple modulators (PFK-1)
Hormonally mediated phosphorylation/dephosphorylation via insulin and glucagon (PFK-2)
Transcriptional regulation - up-regulated by insulin
Function of pyruvate kinase? products produced?
Substrate-level phosphorylation
Catalyses phosphate group transfer of phosphate group of phosphoenolpyruvate and adds it to ADP to create ATP
Results in molecule of pyruvate and molecule of ATP
Very negative delta G -> irreversible under physiological conditions
Hormonal mechanism of regulation of pyruvate kinase?
PKA mediated phosphorylation stimulated by glucagon inactivates pyruvate kinase
PP mediated dephosphorylation stimulated by insulin activates pyruvate kinase
Mechanisms of regulation of pyruvate kinase?
Allosteric regulation by multiple modulators
Hormonally mediated phosphorylation by glucagon
Transcriptional regulation - up-regulated by insulin (L-form only)
What is the function and mechanism of lactate dehydrogenase?
Reduces pyruvate to form L-lactate
-> Oxidises NADH to reform NAD+ allows continued glycolysis and ATP production
Where/how is lactate recycled back to pyruvate?
The liver via the Cori cycle
Main sources forming glucose at the beginning of gluconeogenesis?
Lactate
Triacylglycerols
amino acids