Enzyme inhibitors are defined as any compound, except H+ ions (see pH effects), which decrease the activity when added to an enzyme reaction. Many enzyme inhibitors are known. They are used to kill insects or unwanted plants (herbicides) or animals (rotenone). They are used to prevent browning or preserve "fresh ness" of fruits and vegetables. Many pharmaceutical compounds are designed to kill microorganisms by selectively inhibiting their enzyme systems.
Mechanistically, there are two major groups of enzyme inhibitors. One group inhibits enzymes by reactions involving covalent bond formation (irreversible inhibitors); the other group inhibits enzymes by reversible noncovalent bond formation (reversible inhibitors). Both types are important as they decrease or eliminate enzyme activity.
The rate and extent of inhibition of enzymes by irreversible inhibitors will depend on concentration of inhibitor, concentration of the enzyme, and the specific group modified on the enzyme, as well as pH and temperature. The rate of the inhibition will be relatively slow (minutes or hours) as a covalent bond is formed. The reaction cannot be reversed to regain enzyme activity.
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