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ilanai
#1 Posted : Saturday, July 14, 2018 6:37:17 PM
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Hello!

Why don't noncompetitive inhibitors change the Km? The textbook states that since they bind to a site other than the active site, the Km is unchanged. However, uncompetitive inhibitors still decrease Km even though they bind at a site other than the active site.

Thanks,

Ilana.
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meghaggitt
#2 Posted : Tuesday, July 17, 2018 7:08:30 PM
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Hi Illana,
Non-competitive inhibitors lower Vmax because they cannot be overcome by adding more enzyme. However, they do not lower the affinity of the enzyme for the substrate, so that Km remains the same. Remember the Km is the concentration of substrate at 1/2 Vmax, it is really just a measure of how quickly the enzyme gets to half of its full capacity to catalyze reaction.

Here is a series of graphs that may help if the prep books aren’t able to clarify for you.
http://www.ucl.ac.uk/~ucbcdab/enzass/inhibition.htm

Let me know if you need any more clarification,
Meg
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