Design and Development of Biosensors for the Detection of Heavy Metal Toxicity
Table 2
Type of inhibitors.
Inhibitor type
Binding site on enzyme
Kinetic effect
Competitive inhibitor
An inhibitor that is structurally similar to the substrate cannot undergo the catalytic step, so it wastes the enzymeโs time by preventing S binding, that is, inhibitor competes with substrate for the enzyme-substrate binding site in a dynamic equilibrium process, thus increasing for substrate. Inhibition is reversible using high concentrations of substrate.
is unchanged; โโis increased.
Uncompetitive inhibitor
Binds only to ES complexes at locations other than the catalytic site. Substrate binding modifies enzyme structure, making inhibitor-binding site available. Inhibition cannot be reversed by substrate.
and โโdecreased with the same factor.
Noncompetitive inhibitor
If the inhibitor is not only bound to the E, but also to the E-S complex, at a remote site other than at the catalytic site of the enzyme, thus the active centre is usually deformed and its function is thus impaired, affecting . In this case the substrate and the inhibitor do not compete with each other. Substrate binding is unaltered, but ESI complex cannot form products. Inhibition cannot be reversed by substrate.
appears unaltered; is decreased proportionately to inhibitor concentration.
Mixed inhibitor
AS the noncompetitive, this inhibitor binds at a site other than the active site (E or ES) and causes changes in the overall 3D shape of the enzyme that leads to a decrease in activity. The inhibitor binds to E and ES with different affinity ( not equal to ). Mixed inhibition cannot be overcome by high substrate concentration.
