Enzyme Inhibition Flashcards
What is a reversible inhibitor and what bonds are involved
a substance that binds to an enzyme to inhibit it, but can be reversed
– usually involves formation of non-covalent bonds
What is an irreversible inhibitor and what bonds are involved
a substance that causes inhibition that cannot be reversed
– usually involves formation or breaking of covalent bonds with the enzyme.
name 3 types of reversible inhibition
competitive inhibition
non-competitive inhibition uncompetitive inhibition
Describe the mechanism of irreversible inhibition
the inhibitor binds to the enzyme irreversibly through formation of a covalent bond with the enzyme , permanently inactivating the enzyme
What is diisopropylphosphofluoridate and how does it work
its an irreversible inhibitor that is a prototype for the nerve gas sarin
it permanently inactivates serine proteases by forming a covalent bond with the active site serine.
Describe the mechanism of competitive inhibition
the inhibitor binds only to the free enzyme, not to the ES complex.
• A competitive inhibitor reduces the amount of free enzyme available for substrate binding.
How can lineweaver burk plots diagnose competitive inhibition
Increased inhibitor = steeper slope
y intercept = same, 1/Vmax
x intercept = increases, -1/Km,app
Give an example of a competitive inhibitor
Malonate is a competitive inhibitor of succinate for succinate dehydrogenase
How can competitive inhibition be reversed
The effect of a competitive inhibitor can be overcome with high concentrations of the substrate.
Describe the mechanism of non-competitive inhibition
The inhibitor does not interfere with substrate binding
the inhibitor binds enzyme irrespective of whether the substrate is bound.
why doesn’t noncompetitive inhibition affect the Km
The inhibitor binds equally well to free enzyme and the ES complex, so it doesnt alter apparent affinity of the enzyme for the substrate
How can lineweaver burk plots diagnose non-competitive inhibition
increased inhibitor = steeper gradient
y intercept = increases, 1/Vmax,app
x intercept = same, -1/Km
Give an example of non-competitive
inhibition of pyruvate kinase by alanine
Describe the mechanism of uncompetitive inhibition
In uncompetitive inhibition, the inhibitor binds only to
the ES complex, it does not bind to the free enzyme.
Why do uncompetitive inhibitors have little effect on the reaction rate at low substrate concentrations
At low substrate concentrations, uncompetitive inhibitors have Little effect on the reaction rate Because the lower Km,app of the Enzyme offsets the decreased
Vmax,app
