Diisopropylfluorophosphate (DFP) binds to the active site of acetylcholinesterase (ACE) in the synapses of neurons. When DFP binds to ACE, the ACE enzyme is rendered permanently inactive. This makes DFP a potent toxin, with lethal amounts at less than 100 mg. The interaction between DFP and ACE can best be characterized as:
A) Competitive inhibition
B) Noncompetitive inhibition
C) Irreversible inhibition
D) Partially competitive inhibition
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The binding described involves the inhibitor binding to the enzyme and rendering the enzyme permanently inactive. That’s the definition of irreversible inhibition, making C the correct answer.
A: Competitive inhibitors bind to the active site but bind reversibly: they do not permanently disable the enzyme. By adding very high levels of the normal substrate, the effects of competitive inhibitors can be overcome.
B: Noncompetitive inhibitors bind to a site other than the active site.
D: Partially competitive inhibitors bind to a site other than the active site and allow the enzyme to still have some catalytic activity (typically reduced, but possible to be higher).
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