Non-competitive inhibition

Non-competitive inhibition

Non-competitive inhibition is a type of enzyme inhibition where the inhibitor reduces the activity of the enzyme and binds equally well to the enzyme whether or not it has already bound the substrate.

Mechanism of Action

In non-competitive inhibition, an inhibitor binds to an allosteric site on the enzyme, which is a location other than the active site. This binding causes a conformational change in the enzyme, altering the shape of the active site and preventing the substrate from binding effectively. This results in a decrease in enzyme activity, regardless of the concentration of the substrate.

Unlike competitive inhibition, where the inhibitor and substrate compete for the active site, in non-competitive inhibition, the inhibitor and substrate can bind to the enzyme simultaneously. This is because the inhibitor is not competing with the substrate for the same binding site.

Effects on Kinetics

Non-competitive inhibition has unique effects on the Michaelis-Menten kinetics of an enzyme. It increases the Michaelis constant (Km) and decreases the maximum rate of reaction (Vmax). This is because the inhibitor decreases the overall number of functional enzymes in the solution, reducing the maximum rate of reaction. However, since the inhibitor does not affect the affinity of the enzyme for the substrate, the Km remains unchanged.

Examples

Examples of non-competitive inhibitors include heavy metals such as lead and mercury, which can bind to enzymes and change their shape, rendering them non-functional. Certain drugs, such as antidepressants and antipsychotics, also act as non-competitive inhibitors to increase the levels of certain chemicals in the brain.

See Also

• Enzyme kinetics
• Competitive inhibition
• Uncompetitive inhibition
• Mixed inhibition