Le Chatelier's principle
In the presence of a non-competitive inhibitor, the apparent enzyme affinity is equivalent to the actual affinity. In terms of Michaelis-Menten kinetics, Kmapp = Km. This can be seen as a consequence of Le Chatelier's principle because the inhibitor binds to both the enzyme and the enzyme-substrate complex equally so that the equilibrium is maintained. However, since some enzyme is always inhibited from converting the substrate to product, the effective enzyme concentration is lowered.