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Although some enzymes appear to function according to the older key-lock hypothesis, most apparently function according to the induced-fit theory. Typically, the substrate approaches the enzyme surface and induces a change in its shape that results in the correct alignment of the catalytic groups.
In the induced fit model, both the substrate enzyme’s active site undergoes conformational changes up until the substrate is fully attached to the enzyme.
Induced-Fit Model Definition The induced-fit model is a model for enzyme–substrate interaction to depict the dynamic interaction between an enzyme and its substrate. Both the enzyme and the substrate molecules undergo conformational changes to achieve optimal binding and catalytic efficiency.
The modified model of enzyme activity is known as the ‘induced-fit hypothesis’ Although it is very similar to the lock and key hypothesis, in this model the enzyme and substrate interact with each other:
Therefore, the Induced Fit Model offers a detailed and sequential explanation of the dynamic interactions between enzymes and substrates, emphasizing the adaptability and specificity of enzymes in biochemical reactions.
The induced fit model states an substrate binds to an active site and both change shape slightly, creating an ideal fit for catalysis. When an enzyme binds its substrate it forms an enzyme-substrate complex.
These two extreme possibilities are known as induced fit and conformational selection respectively. The concept of induced fit was introduced by Daniel Koshland and was first used to describe the formation of the catalytically competent conformation of an enzyme active site upon ligand binding .
The induced fit model explains both the features of the enzyme that is the specificity and flexibility. There were experimental evidences to support the changes in the active site confirmation upon the approach of the substrate and finally getting transformed into the product.
The lock-and-key model portrays an enzyme as conformationally rigid and able to bond only to substrates that exactly fit the active site. The induced fit model portrays the enzyme structure as more flexible and is complementary to the substrate only after the substrate is bound.
Recent studies on DNA polymerization have illuminated the role of substrate-induced conformational changes in enzyme specificity by showing that the rate at which the enzyme opens to release the bound substrate is a key kinetic parameter.