Control Mechanism I Flashcards
Two ways to control enzyme activity?
Course control and fine control
What is course control?
Changes in the amount of an enzyme
What is fine control?
Changes in the activity of an enzyme without changing the amount
How does fine control differ to course control?
Occurs more rapidly and its reversible
What is the definition of Km?
Substrate concentration that gives you half Vmax
What type of enzyme control do inhibitors have?
Fine control
What are inhibitors?
Chemicals that reduce the rate of enzymic reactions
What are the two types of inhibitors?
Irreversible and reversible
How do irreversible inhibitors work?
Covalent modification usually at the active site
Give an example of irreversible inhibition.
DFP that covalently modifies a serine in the active site of acetylcholinesterase
What is DFP?
Diisopropylphosphofluoridate
What are the two classes of reversible inhibition?
Competitive and non-competitive
How does competitive inhibition work?
Inhibitors bind to active site but do not react, excess substrate can overcome
Give an example of competitive inhibition.
Succinate dehydrogenase inhibited by malonate
How does a competitive inhibitor effect Vmax and Km?
Vmax is unchanged
Km is increased
Why does Km increase with competitive inhibitors?
More substrate is needed to achieve half Vmax
How many sites does a non-competitive inhibitor have?
2 sites - active and inhibitor
How does non-competitive inhibition work?
Inhibitor binding does not prevent substrate binding
Give an example of non-competitive inhibition.
Fructose 1,6 bisphosphatase inhibited by AMP
How does non-competitive inhibition affect Vmax and Km?
Vmax is reduced
Km is unchanged
Why does non-competitive inhibition reduce Vmax?
Less enzyme-substrate complexes can form
Why does non-competitive have no affect on Km?
No competition for substrate binding
Describe linear pathway feedback regulation.
When end product accumulates it inhibits the first step of pathway (reversible)
