What is the Difference Between Lock and Key and Induced Fit?

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The lock-and-key model and the induced-fit model are two theories that explain the mode of an enzyme-substrate interaction. The main differences between these two models are:

  1. Conformation of the Enzyme:
  • In the lock-and-key model, the enzyme is conformationally rigid and can only bind to substrates that exactly fit the active site.
  • In the induced-fit model, the enzyme structure is more flexible, and the active site is complementary to the substrate only after the substrate is bound, leading to a conformational change in the enzyme.
  1. Substrate Binding:
  • In the lock-and-key model, the active site of the enzyme is the complement of the substrate, and it precisely fits the substrate.
  • In the induced-fit model, the active site of the enzyme does not completely fit the substrate, and it undergoes a conformational change to improve binding.
  1. Mechanism of Action:
  • The lock-and-key model is more suitable for explaining the specificity of an enzyme, as it requires a perfect fit between the substrate and the enzyme's active site.
  • The induced-fit model is more suitable for explaining the mechanism of noncompetitive inhibitors, as it allows for the possibility that the active site can change shape to accommodate a substrate.

Both models are important for understanding how enzymes increase the rate of biological reactions through precise binding of the substrate to the active site. However, they differ in their explanations of the conformation of the enzyme and the process of substrate binding.

Comparative Table: Lock vs Key vs Induced Fit

The Lock and Key model and the Induced Fit model are two different theories that explain the mode of enzyme-substrate interaction. Here is a comparison table highlighting the key differences between the two models:

Feature Lock and Key Model Induced Fit Model
Definition The Lock and Key model refers to a second model for enzyme-substrate interaction in which the active site of the enzyme is the complement of the substrate, and hence, it precisely fits to the substrate. The Induced Fit model refers to a model for enzyme-substrate interaction in which the active site of the enzyme does not completely fit to the substrate; it undergoes a conformational change to improve binding.
Active Site The active site is static and complementary to the substrate. The active site is not static and has to undergo a conformational change to improve binding.
Substrate Binding The substrate and the active site of the enzyme are complementary in shape at the beginning. The binding of the substrate with the active site of the enzyme induces the modification of the active site.
Specificity The model emphasizes the specificity of the active site for the substrate. The model highlights the dynamic nature of the enzyme-substrate interaction.

Both models depend on the degree of precise binding of the substrate to the active site of the enzyme, and they are important in describing how enzymes increase the rate of a biological reaction through substrate binding. However, the main difference between the two models is the mechanism of substrate binding and the conformational changes in the active site of the enzyme.