Enzyme inhibition Flashcards
(50 cards)
Two main categories/classes of inhibitors
Irreversibel
Reversible
Definition of inhibitors
Molecules that interfere with catalysis, slowing or halting enzymatic reactions
3 types of reversible inhibitors
Competitive
Uncompetitive
Noncompetitive
Difference between uncompetitive and noncompetitive inhibition
Uncompetitive binds only when the substrate is bound and it binds to additional binding site on active site
Noncompetitive binds only to allosteric site and in all conditions (so when substrate is bound and when it is not)
When does the uncompetitive inhibitor bind?
Only after substrate is bound
When does the noncompetitive inhibitor bind?
In all conditions, substrat bound or not bound
What does sulphanilamide mimic the structure of? and thus inhibits the metabolisation of
PABA (p-aminobenzoic acid)
How is the rate of reaction effected by the inhibitor?
The rate decreases
Due to decrease in affinity
More substrate is needed
What is Km?
Substrate concentration at half Vmax
What happens to the Vmax during competitive inhibition?
Nothing
It is not changing because as substrate increases inhibition decreases eventually to the point where it disappears
What happens to the Km during competitive inhibition?
Increases
Does competitive inhibition affect catalysis?
No, does not effect the catalysis and the process
With competitive inhibitors how do the Vmax compare to reaction with no inhibitor?
They are the same
In a noncompetitive inhibitor how is the Km effected?
No change
Because the binding site is the same and the binding is the same (affinity for binding is the same)
In a noncompetitive inhibitor how is the Vmax effected?
Decrease
Activity of enzyme is decreased
What does the noncompetitive inhibitor affect? The affinity to bind or the enzymatic activity?
Enzymatic activity
Can a change in conformation cause and enzyme to have affinity for a different substrate?
Yes
Which inhibitor can be used to map an active site?
Irreversible inhibitor
Affinity labels
3 major types of irreversible inhibitors
Group specific reagents
Affinity labels (or reactive substrate analogs)
Suicide inhibitors (or mechanism-based inhibitors)
Why is it group specific reagents irreversible inhibition?
Only interacts with one specific amino acid in a specific position in the compound (the ex serine of the active site)
How does the affinity labelling irreversible inhibitor work?
Part of inhibitors attaches to part of the enzyme
How does the suicide irreversible inhibitor work?
Binds as a substrate and is then modified by enzyme into an irreversible inhibitor
What kind of inhibitor is penicillin?
Suicide irreversibel inhibitor
What are transition state inhibitors?
Inhibitor that resembles the transition state substrate
