Enzyme Kinetics III: Noncompetitive Inhibition

Abstract

In competitive inhibition (according to the kinetic model of Procedure 19), the inhibitor molecule reacts reversibly with the enzyme at the site normally occupied by the substrate. There are several mechanisms of noncompetitive inhibition. In one such mechanism the inhibitor can alter the activity of the enzyme without blocking the active site. In other words, I (the inhibitor) can combine with E (the enzyme) or ES (the enzyme-substrate complex), the dissociation constant in either case being denoted by K_I. As in the previous discussions, we denote by K_M the Michaelis constant for the reaction E + S ⇌ ES.