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Enzymes
can be inhibited competitively, when the
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substrate
and inhibitor compete for binding to the same
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active
site or noncompetitively, when the inhibitor binds
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somewhere
else on the enzyme molecule reducing its
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efficiency.
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The
distinction can be determined by plotting enzyme
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activity
with and without the inhibitor present.
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Competitive
Inhibition
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In
the presence of a competitive inhibitor, it takes a higher
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substrate
concentration to achieve the same velocities that
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were
reached in its absence. So while Vmax can still be
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reached
if sufficient substrate is available, one-half Vmax
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requires
a higher [S] than before and thus Km is larger.
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