Active site

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The active site on an enzyme is the three-dimensional region that allows the binding of substrate molecules. The active site is of a specific shape only allowing certain substrate molecules to bind to it. This explains the specific nature of enzymes and how they are only able to cataylse certain reactions [1].

Active site of an enzyme is a small 3 dimensional portion of an enzyme where substrates bind. The substrates slots into the active site which is lined by amino acid residues. Once the active site is bound to substrate, an enzyme substrate complex is formed which enables the substrate to be broken down.

The substrate binds to the enzyme's active site via the 'lock and key hypothesis' meaning the substrate shape is complementary to that of the enzyme's active site and hence fits. However, sometimes the active site can alter its shape to accommodate the substrate and this is called the 'induced fit theory.


  1. Berg Jeremy M., Tymoczko John L., Stryer Lubert., (2007) Biochemistry, Sixth Edition, New York, W.H. Freeman and Company.
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