Problem 9 What are the three classes of re... [FREE SOLUTION]

Chapter 7: Problem 9

What are the three classes of reversible inhibitors? Briefly describe them and their effects on apparent \(K_{\mathrm{m}}\) and \(v_{\max }\)

Short Answer

Expert verified

Answer: The three classes of reversible inhibitors are competitive, noncompetitive, and uncompetitive inhibitors. 1. Competitive inhibition: The inhibitor competes with the substrate for binding to the enzyme's active site, increasing apparent \(K_m\) while \(v_{\max}\) remains unchanged. 2. Noncompetitive inhibition: The inhibitor binds to the enzyme at a site other than the active site and affects both the free enzyme and enzyme-substrate complex, causing the \(v_{\max}\) to decrease while the apparent \(K_m\) remains unchanged. 3. Uncompetitive inhibition: The inhibitor binds only to the enzyme-substrate complex at a site different from the active site, resulting in a decrease in both apparent \(K_m\) and \(v_{\max}\).

Step by step solution

Identify the reversible inhibitors classes

The three classes of reversible inhibitors are competitive, noncompetitive, and uncompetitive inhibitors.

Describe competitive inhibition

In competitive inhibition, the inhibitor resembles the substrate and competes with it for binding to the active site of the enzyme. This forms an enzyme-inhibitor (EI) complex, preventing the formation of the enzyme-substrate (ES) complex. The effect on enzyme kinetics is an increase in apparent \(K_m\), while the \(v_{\max}\) remains unchanged. This is because the inhibitor's presence reduces the affinity of the enzyme for the substrate (higher apparent \(K_m\)), but once the substrate outcompetes the inhibitor, the enzyme can still function at its maximum velocity. \[\frac{v}{[S]}=\frac{v_{\max }}{K_{\mathrm{m}}(1+\frac{[I]}{K_{\mathrm{i}}})+[S]}\]

Describe noncompetitive inhibition

In noncompetitive inhibition, the inhibitor binds to the enzyme at a site other than the active site, and can bind both the free enzyme and the enzyme-substrate complex (ES). The binding of the inhibitor alters the enzyme's conformation, reducing its catalytic activity. In this case, the apparent \(K_m\) remains unchanged, while the \(v_{\max}\) decreases. This indicates that the affinity of the enzyme for its substrate is not impacted, but the overall conversion rate is negatively affected by the inhibitor. \[\frac{v}{[S]}=\frac{v_{\max }}{\frac{K_{\mathrm{m}}}{1-\frac{[I]}{K_{\mathrm{i}}}}+[S]}\]

Describe uncompetitive inhibition

In uncompetitive inhibition, the inhibitor only binds to the enzyme-substrate (ES) complex at a site different from the active site. Binding of the inhibitor does not prevent the formation of the ES complex but hinders the enzyme's ability to convert the substrate to product. The effect on enzyme kinetics is a decrease in both apparent \(K_m\) and \(v_{\max}\). The decrease in \(K_m\) indicates increased affinity between the enzyme and substrate in the presence of an inhibitor, while the decreased \(v_{\max}\) shows that the overall catalytic activity of the enzyme is reduced. \[\frac{v}{[S]}=\frac{v_{\max }}{K_{\mathrm{m}}(1+\frac{[S]}{K_{\rm{i}}})+[S]}\]

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What are the three classes of reversible inhibitors? Briefly describe them and their effects on apparent \(K_{\mathrm{m}}\) and \(v_{\max }\)

Short Answer

Step by step solution

Identify the reversible inhibitors classes

Describe competitive inhibition

Describe noncompetitive inhibition

Describe uncompetitive inhibition

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