Lecture 10 - enzyme regulation Flashcards
how are metabolic enzymes different fron michaelis-menten enzyme kinetics
show a sigmoidal v0 vs [S] plot instead to hyperbolic
how are metabolic enzymes different fron michaelis-menten enzyme kinetics
show a sigmoidal v0 vs [S] plot instead to hyperbolic
what are ‘allosteric’ enzymes
activity of enzyme controlled by conformational changes caused by small molecules
(can be substrates or regulator)
mostly have quaternary structure
show cooperativity between subunits
what is non cov allosteric regulation
allosteric inhibitors/activators binding to a second regulatory site to cause conformational change
what is cooperativity
a substrate binding to one active site changes affinity of binding at other sites (usually makes enzyme more active)
what does binding of an activator to allosteric site cause
stabilises the active form (R or relaxed form)
what does binding of an inhibitor to allosteric site do
stabilises inactive form (T or tight form)
what is PFK-1
phosphofructose kinase 1
an allosteric enzyme
what does PFK-1 regulate
conversion of fructose-6-phosphate to fructose-1,6-bisphosphate
what is the allosteric activator for PFK-1
ADP
what is the allosteric inhibitor for PFK-1
PEP
competitive inhibitors mode of action
- binds only to free enzyme
- increased Km
- Vmax stays same
uncomptetitive mode of action
- binds only to E-S complex
- decreases Vmax and Km
- inc affinity cuz when inhibitor bound, it stops the ES complex from releasing the substrate
- but product cant be made, so decreased Vmax
non competitive mode of action
- binds to BOTH dree enzyme and ES complex
- doesnt change Km (cuz substrate can still bind freely)
- decreases Vmax (cuz when inhibiotr bound, stops the product from being made
- adding more substrate doesnt do anythin
