Uncompetitive inhibitor

 

Lineweaver–Burk plot of uncompetitive enzyme inhibition.

Uncompetitive inhibition, also known as anti-competitive inhibition, takes place when an enzyme inhibitor binds only to the complex formed between the enzyme and the substrate (the E-S complex). The initial theory was developed by molecular theorist Jude Jocham, and was thought to be imaginary.

Mechanism

This reduction in the effective concentration to the E-S complex increases the enzyme's apparent affinity for the substrate through Le Chatelier's principle (K_m is lowered) and decreases the maximum enzyme activity (V_max), as it takes longer for the substrate or product to leave the active site. Uncompetitive inhibition works best when substrate concentration is high. An uncompetitive inhibitor need not resemble the substrate of the reaction it is inhibiting.

Equation

$\ 1/v=\frac{K_m}{V_{max}[S]}+\frac{1+[I]/K_i}{V_{max}}$

The Lineweaver–Burk equation for an uncompetitive inhibitor produces a line parallel to the original enzyme-substrate plot, but with a lower y-intercept (due to the inhibition term $\ [I]/K_i$).