Question

RECAQ. If we made a Lineweaver-Burk plot of an irreversible inhibitor, which type of reversible inhibition would it be most likely to resemble?

Short answer

Non-competitive inhibition.

Step-by-step solution

Understand the Lineweaver-Burk plot

The Lineweaver-Burk plot is a double-reciprocal plot of enzyme kinetics that plots 1/[S] (the reciprocal of substrate concentration) against 1/V (the reciprocal of the reaction rate). It is used to determine the type of inhibition affecting enzyme action.

Review types of reversible inhibition

There are three main types of reversible inhibition: competitive, non-competitive, and uncompetitive. Each type affects the enzyme kinetics in a distinct way.

Compare irreversible inhibition to reversible inhibition

Irreversible inhibitors bind permanently to the enzyme, reducing the number of active enzyme molecules. This effect is similar to non-competitive inhibition because it does not compete with the substrate for the active site.

Determine resemblance on the Lineweaver-Burk plot

On a Lineweaver-Burk plot, non-competitive inhibition shows an increase in the apparent K_m (Michaelis constant remains the same) but a decrease in V_max (maximum reaction velocity). Irreversible inhibition shows a similar pattern.

Conclude the type of reversible inhibition

Irreversible inhibition most closely resembles non-competitive inhibition when viewed on a Lineweaver-Burk plot due to the similar effects on enzyme kinetics.

Key concepts

Enzyme Kinetics

Enzyme kinetics is the study of the rates at which enzyme-catalyzed reactions occur. It helps us understand how different factors affect the speed and efficiency of enzymatic reactions. One of the main tools used in enzyme kinetics is the Lineweaver-Burk plot. This double-reciprocal plot allows us to understand how variations in substrate concentration and reaction rates provide insights into enzyme behaviors and inhibition types.

To create a Lineweaver-Burk plot, you plot the reciprocal of the substrate concentration \( \frac{1}{[S]} \) against the reciprocal of the reaction rate \( \frac{1}{V} \). Through this plot, we can identify how inhibitors affect enzymes.

Irreversible Inhibition

Irreversible inhibition occurs when an inhibitor permanently binds to an enzyme, rendering it inactive. This binding often happens through covalent bonds, which means that the enzyme can no longer participate in reactions.

Once an enzyme is irreversibly inhibited, the effect cannot be reversed by simply increasing substrate concentration. This causes a permanent decrease in the number of active enzyme molecules available.

Non-Competitive Inhibition

In non-competitive inhibition, the inhibitor binds to an enzyme at a site other than the active site. This binding changes the shape of the enzyme, which affects its function and diminishes the overall reaction rate.

The key characteristic of non-competitive inhibition is that it cannot be overcome by increasing substrate concentration. It decreases the V_max without affecting the K_m, meaning the enzyme's affinity for the substrate remains the same.

Reversible Inhibition

Reversible inhibition involves inhibitors that bind to enzymes non-covalently. This means their effects can be reversed by removing the inhibitor or by adding more substrate.

There are three main types of reversible inhibition: competitive, non-competitive, and uncompetitive. Each type affects enzyme kinetics differently and results in distinctive changes on a Lineweaver-Burk plot.