Non-competitive inhibition is a type of reversible inhibition because the enzyme is not permanently altered. In this type of inhibition, product formation is prevented for a limited time.
The substrate can freely bind the active site in non-competitive inhibition. This is because the inhibitor is not attempting to bind the active site for the substrate that normally binds the enzyme.
The inhibitor binds a separate site known as the allosteric site, and changes the ability of the enzyme to catalyze transformation of the substrate to the product. This enzyme-inhibitor complex is strong because it is not competing with the substrate for binding.
In non-competitive inhibition, Km is constant (concentration of substrate at one-half Vmax) because adding more substrate will not affect the reaction kinetics. The binding of the substrate is not affected.
Though the enzyme is not permanently altered, it does change conformation while the inhibitor is bound, preventing the enzyme from catalyzing the transformation from substrate to product.
Though Km remains unchanged, non-competitive inhibition results in a lower Vmax, which is a lower maximum rate of reaction. This is because the enzyme is less able to convert the substrate into product at the active site and can no longer function as well as an uninhibited enzyme.
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