What is the difference between the lock-and-key model of enzyme action and the induced-fit model
The Correct Answer and Explanation is:
The lock-and-key model and the induced-fit model are two theories that describe how enzymes interact with substrates, but they differ in their explanation of how the enzyme’s active site accommodates the substrate.
Lock-and-Key Model:
The lock-and-key model, proposed by Emil Fischer in 1894, suggests that the enzyme’s active site has a specific, rigid shape that exactly matches the shape of the substrate, much like a key fitting into a lock. In this model, the substrate binds perfectly to the enzyme’s active site without any alteration in the structure of the enzyme. The binding of the substrate is precise and highly specific. According to this model, the enzyme is already in a perfectly complementary state to the substrate before the reaction takes place.
Induced-Fit Model:
In contrast, the induced-fit model, proposed by Daniel Koshland in 1958, argues that the enzyme’s active site is flexible and can undergo a conformational change when the substrate binds. Rather than the substrate simply fitting into a pre-existing, rigid active site, the enzyme’s structure is slightly altered to better fit the substrate once it binds. This model suggests that the enzyme’s flexibility allows it to bind to a wider variety of substrates with high specificity. The induced-fit model emphasizes the dynamic interaction between the enzyme and the substrate, where the enzyme’s shape adapts upon substrate binding.
Key Differences:
- Enzyme Active Site Structure: In the lock-and-key model, the active site is rigid, whereas in the induced-fit model, it is flexible and can change shape.
- Binding Mechanism: The lock-and-key model assumes a perfect fit from the beginning, while the induced-fit model proposes that the enzyme adjusts to accommodate the substrate.
- Flexibility: The induced-fit model highlights the enzyme’s ability to adapt, making it more versatile in binding substrates of different shapes, whereas the lock-and-key model assumes a fixed, unchanging active site.
In summary, the lock-and-key model emphasizes a static interaction, while the induced-fit model focuses on the dynamic, adaptable nature of the enzyme-substrate interaction.
