Enzyme inhibition is the hindrance of the enzyme activity by an enzyme inhibitor. An inhibitor is a substance, other than the enzyme, that attaches itself onto the enzyme thereby inhibiting the enzyme affinity to the substrate. The inhibitor attaches itself to the binding site of the enzyme rendering the enzyme incompatible to the substrate since the enzymes are specific to the substrate onto which they bind to catalyze metabolic processes.
Enzyme inhibition can lead to allergies when exposed to certain types of foods. The inability to produce the right enzyme for substrate metabolism may lead to complex problems such as lactose intolerance.
There are three types of enzyme inhibition namely:
Competitive enzyme inhibition
In this type of inhibition, the inhibitor binds itself to the catalytic site and competes with the substrate for the same binding site. The inhibitor has structural similarity to the substrate. It reduces enzymes by forming Enzyme-Inhibitor complex and consequently;
Vmax remains unchanged since at high levels of substrate concentration [S], all the inhibitor is displaced by the enzyme
Km is increased since higher substrate concentrations are required to reach maximum velocity
Competitive inhibition: inhibitor binds itself to the catalytic site and competes with the substrate Click To Tweet
Non-competitive enzyme inhibition
The inhibitor binds to both the Enzyme [E] and the Enzyme-Substrate [ES] complex. The inhibitor need not to be structurally similar to the substrate. As a result of the action of this type of inhibitor, we make these two observations:
Vmax reduces since, at high substrate concentration levels, the inhibitor is still bound
Km increases since higher substrate concentration [S] is necessary to reach the lower maximum velocity
Uncompetitive enzyme inhibition
Here, the inhibitor binds directly to the Enzyme-Substrate [ES] complex and not necessarily at the active binding site. The attachment distorts the physical conformation of the enzyme making it unfit for its substrate hence reducing the enzyme’s affinity to the substrate. The inhibitor does not necessarily have to structurally resemble the substrate.
In this type of inhibition, the Vmax is reduced since the amount of ESI formed depends on the concentration of the inhibitor.