Enzyme active site

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The active site of an enzyme is the region on which thesubstrate (and any present cofactors) are bound during catalysis. There can be either one or more substrate molecules and after binding to the enzyme the enzyme-substrate complex is formed. An enzyme's active site is the the location that directly lowers the change in Gibbs free energy of a reaction, producing faster rates of reaction as a result[1]. All reactions occur on the active site which is a 3D cleft or groove and the specificity of enzymes is due to the specific structural regions on the active site. The specificity can be explained by either of two binding methods:

  1. lock and key mechanism: whereby the substrate fits exactly on to the active site due to its complementary shape. 
  2. induced fit mechanism: whereby upon binding the active site changes its shape so as to bind exactly with the substrate.

At the end of catalysis, the enzyme and its active site remain unchanged and release the products.

The active site of an enzyme can be altered by non-competitive inhibitors which changes the shape by binding elsewhere on the enzyme, thus disabling its ability to bind with the substrate [2] [3].


  1. Berg J, Tymoczko J and Stryer L. (2006) Biochemistry, 6th Edition, New York, W.H. Freeman and Company
  2. Alberts, B., Johnson, A., Lewis, J., Kaff, M., Roberts, K. and Walter P. (2008) Molecular Biology of the Cell Fifth Edition. Abingdon: Garland Science.
  3. Alberts, B., Bray, D., Hopkin,K., Johnson, A., Lewis,J,Raff, M.,Roberts,K.,Walter,P.,(2004) Essential Cell Biology Second Edition.New York: Garland Science

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