lecture 7 - enzymes Flashcards
What does the effect of pH have on the enzyme?
protein structural changes - affects the state of protonation within the active site
What effect can the pH have on a substrate?
May affect the protonation states of the substrate too
How does the temperature affect the enzyme?
Increase the flexibility in the protein backbone , becomes more dynamic , increased rate. Eventually too flexible and denatures
What are the two types of non- covalent regulators?
- simple inhibition
- allosteric inhibition
What are the 3 types of simple , non - covalent regulation
- competitive
- non-competitive
- uncompetitive
Is non- covalent regulation reversible?
yes
what is the effect of competitive inhibition on the Vmax?
nothing
What is the effect of competitive inhibition on the Km?
Km increases ( apparent Km)
What is the effect of competitive inhibition on the dissociation constant?
increases
What happens to the Lineweaver Burk plot with competitive inhibition?
Cross at the same point on the y axis
What is the mechanism of noncompetitive inhibition?
- Binds to enzyme but not at active site
- changes the shape of enzyme and active site
- substrate cannot fit into active site
What is the effect of non - competitive inhibitor on the Vmax?
Vmax is reduced
What is the effect of the non - competitive inhibitor on the Km?
The Km is not affected
What form of the enzyme can thE non-competitive inhibitor effect?
- Free enzyme
- ES complex
What affects are caused by non-competitive inhibition on the Lineweaver Burk plot?
Both cross the x axis at the same place
What is the mechanism of the uncompetitive inhibitor?
When the inhibitor binds only to the ES to make ESI
Where is uncompetitive inhibition found?
With an enzyme that catalysis a 2 step reaction
What effects doe uncompetitive inhibition have on the Km and Vmax?
both decreased
what is the advantage of Allosteric inhibition over simple inhibition?
Highly sensitive and can drastically increase or decrease the product.
What is the most common form of allosteric inhibition
non competitive
Does allosteric inhibition follow the Michaelis Menton curve?
No , it gives a sigmoidal curve. Inhibitor or activator pushes the sigmoidal curve one way or another, pushing to higher of lower substrate concentrations
what are the advantages of covalent regulation?
Dramatic activation or inactivation/can you completely switch it on or off
What are the two types of covalent regulation?
- reversible, inactivation or activated
- irreversible, enzyme may be activated by being cleaved
How do you classify the 6 types of enzyme s
- Oxo-reductases
- Transferases
- Hydrolases
- lyases
- isomerases
- ligases
What to measure in awn enzyme assay?
Initial product // disappearance of substrate
An noncompetitive inhibitor
- changes the shape of enzyme and active site
- does not have a structure like substrate
What can a noncompetitive inhibitor do?
- Bind to both the free enzyme and enzyme substrate complex
Allosteric inhibition
Show co-operative binding.
Has binding sites and can switch between two forms ; active vs inactive
Does allosteric inhibition reduced V or Vmax
reduces the rate but not the Vmax.
Why do allosteric inhibitors have such a big effect on rate?
A small change In the inhibitor concentration gives a big inhibition
what shape are allosteric proteins?
Allosteric proteins tend to be oligomeric
Active form vs inactive form of allosteric inhibition
active form - bound in via the substrate. inactive , inhibitor bound to allosteric site
What is a example of irreversible covalent enzymes?
proteases . synthesised as inactive precursors- Zymogens , then cleaved to produced the active enzyme
