Mechanism of Enzyme Action

Mechanism of Enzyme Action

Lock Key Hypothesis of an Enzyme

  • Proposed by Emil Fischer.
  • According to him enzyme its substrate have a complementary shape.
  • The specific substrate molecules are bound to a specific region of the enzyme molecule which is known as the active site.
  • The enzyme reacts with the substrate molecule to form an intermediate complex.
  • This complex will react to release yield the products of the reaction.
  • According to this hypothesis, a particular lock can be opened by a particular key which is specially designed to open it.
  • The notched portion of the key act as an active site because reaction or unlocking to lock takes place here.
  • Only specific molecules can fit correctly into the specific active sites.
  • A key or enzyme can open several types of substrates as they have engineering designs or peptide linkages so during the complex formation substrate fit exactly to the active site of the enzyme as a key fits into a lock.

Induced Fit Hypothesis of an Enzyme

  • Proposed by Dan Koshland.
  • The active site of the enzyme does not initially exist in a shape complementary to its substrate.
  • It is induced to assume the complementary shape according to the substrate.
  • So, there is a precise fit between the enzyme and the substrate.
  • It is a type of gloves and hand relationship between the enzyme and substrate.
  • Monod and co-workers given the allosteric model of enzymes to explain that an enzyme can have two or more binding sites that interact practically with each other.

Factors Affecting Enzyme Activity

Substrate Concentration

Enzyme Concentration


Hydrogen ion Concentration

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