9.12.3 Nature of Enzyme Action

Each enzyme (E) has a substrate (S) binding site in its molecule so that a highly reactive enzyme-substrate complex (ES) is produced. This complex is short-lived and dissociates into its product(s) P and the unchanged enzyme with an intermediate formation of the enzyme-product complex (EP). The formation of the ES complex is essential for catalysis. E + S ˆ ˆ ˆ† ‡ ˆ ˆˆ ES ⎯ →⎯ EP ⎯ →⎯ E + P

The catalytic cycle of an enzyme action can be described in the following

  • First, the substrate binds to the active site of the enzyme, fitting into the active site.
  • The binding of the substrate induces the enzyme to alter its shape, fitting more tightly around the substrate.
  • The active site of the enzyme, now in close proximity of the substrate breaks the chemical bonds of the substrate and the new enzyme- product complex is formed.
  • The enzyme releases the products of the reaction and the free enzyme is ready to bind to another molecule of the substrate and run through the catalytic cycle once again.


Related posts

Leave a Comment