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An Allosteric Site Is a Second Binding Site Away From the Active Site
- An enzyme's active site is where the substrate binds and the reaction is catalysed.
- Many enzymes also have an allosteric site, a separate binding site located elsewhere on the enzyme.
- Only specific molecules, called allosteric regulators, bind there, and they are often products or intermediates of a metabolic pathway.
- Binding at the allosteric site is reversible, so the enzyme returns to its original state once the regulator leaves.
Definition
Allosteric site
A site on an enzyme other than the active site, where specific molecules can bind to regulate enzyme activity.
Analogy
- Think of the enzyme as a flexible tool.
- Binding at the allosteric site is like turning a screw on the tool, changing its shape and how well it works.
Binding at the Allosteric Site Changes the Enzyme's Shape
- When a regulator binds to the allosteric site, it triggers a conformational change in the enzyme.
- This reshapes the active site, either boosting or blocking its ability to catalyse the reaction.
- Allosteric activation
- An activator reshapes the active site so it binds substrate more readily, raising enzyme activity.
- Allosteric inhibition
