Open Question
Draw the representative lines for enzyme activity for an inhibitor with α > α' and a separate line with α < α'.
7. Enzyme Inhibition and Regulation
Mixed Inhibition
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When a mixed inhibitor favors binding to the enzyme-substrate complex (ES) over the free enzyme (E), the apparent substrate affinity (apparent Km) is:
A
Greater than the substrate affinity for E (Km)
B
Less than the Km
C
Equal to the Km
Verified step by step guidance1
Understand the concept of mixed inhibition: Mixed inhibitors can bind to both the enzyme (E) and the enzyme-substrate complex (ES), but they have different affinities for each.
Recall that the apparent Km (denoted as Km') is the substrate concentration at which the reaction velocity is half of the maximum velocity in the presence of an inhibitor.
In mixed inhibition, if the inhibitor favors binding to the ES complex more than to the free enzyme, it affects the apparent Km.
When the inhibitor binds more effectively to the ES complex, it stabilizes the ES complex, which can lead to a decrease in the apparent Km, indicating increased substrate affinity.
Therefore, when a mixed inhibitor favors binding to the ES complex, the apparent Km is less than the Km for the free enzyme, meaning the substrate affinity appears to increase.
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