12.2 Mechanism of enzyme catalysis

  Surface Chemistry

• The most accepted mechanism of enzyme catalyzed reaction is known as Lock and Key mechanism.

• Enzymes are highly specific in their action. The specificity of the enzymes is due to the presence of some specific regions, called the active sites, on their surface.

• These active sites are associated with some functional groups such as ${N{H_2}}$, $COOH$, $OH$, $SH$ etc. which form weak bonds such as hydrogen bonds, van der Waals attraction etc., with the substrate (reactant) molecules.

• The shape of the active site of any given enzyme is like a cavity such that only a specific substrate can fit into it, in the same way as one key can fit into a particular lock.

• This specific binding leads to the formation of an enzyme-substrate complex which accounts for the high specificity of enzyme-catalyzed reactions.

• Once the proper orientation has been achieved, substrate molecules react to form the products in two steps.

• Since the product molecules do not have any affinity for the enzyme surface, they at once leave the enzyme surface making room for the fresh substrate molecules to bind to the active sites. The rate of formation of product depends upon the concentration of ES.