Biology – Mode of action of enzymes | e-Consult

Enzymes are primarily globular proteins, meaning their polypeptide chains are folded into complex three-dimensional structures. This folding is crucial for their catalytic activity. The specific three-dimensional shape of an enzyme creates a region called the active site.

The active site is a pocket or cleft formed by specific amino acid residues. The precise arrangement of these amino acids creates a complementary shape to the substrate – the molecule the enzyme acts upon. This 'lock and key' or 'induced fit' model ensures that only the correct substrate can bind to the active site.

The structure of the enzyme is essential for catalysis because it:

• Provides a specific binding site for the substrate.
• Can bring reactants closer together, increasing the effective concentration.
• Can distort the substrate, straining chemical bonds and making them easier to break.
• Can provide an alternative reaction pathway with a lower activation energy.

Without the precise three-dimensional structure, the enzyme would not be able to bind to the substrate effectively, and therefore would not be able to catalyze the reaction. The globular nature of the protein allows for the formation of these specific shapes and the presence of various functional groups within the active site.