# Mixed inhibition

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Mixed inhibition refers to a combination of two different types of reversible enzyme inhibitioncompetitive inhibition and uncompetitive inhibition. The term 'mixed' is used when the inhibitor can bind to either the free enzyme or the enzyme-substrate complex. In mixed inhibition, the inhibitor binds to a site different from the active site where the substrate binds. Mixed inhibition results in an decrease in the apparent affinity of the enzyme for the substrate (${\displaystyle K_{m}^{app}>K_{m}}$) and a decrease in the apparent maximum enzyme reaction rate (${\displaystyle V_{max}^{app}>V_{max}}$).[1]

Mathematically, mixed inhibition occurs when the factors α and α’ (introduced into the Michaelis-Menten equation to account for competitive and uncompetitive inhibition, respectively) are both greater than 1.

In the special case where α = α’, noncompetitive inhibition occurs, in which case ${\displaystyle V_{max}^{app}}$ is reduced but ${\displaystyle K_{m}}$ is unaffected. This is very unusual in practice[1]

## References

1. Functional Metabolism: Regulation and Adaptation. Wiley-IEEE. 2004. p. 12. ISBN 047141090X.