Lock and Key Model vs Induced Fit Model

Enzymes are biocatalysts. They increase the rate of biochemical reaction by decreasing the activation energy. The specific substrate binds with the enzyme at the active site and converts it into the product. The proper binding of the substrate at the active site is the key step in an enzyme-catalyzed reaction. To explain the enzyme-substrate binding, two models i.e., the lock and key model and induced fit model are extensively used.

Read more about the lock and key model and the induced fit model.

Video lesson

Lock and key model vs induced fit model

The lock and key model was proposed by German chemist Emil Fisher in 1894 and based on the fact that as one specific key can open a specific lock, similarly one specific substrate can bind to one specific enzyme. On the other hand, the induced fit model describes the conformational changes in the active site of the enzyme during the binding with the substrate.

Although these models are used to explain the enzyme-catalyzed reactions, there are some differences and similarities between both models.

Similarities between Lock and key model and induced fit model

The main similarities between both models are:

• Both models describe an enzyme-catalyzed reaction.
• They explain substrate binding to the active site of an enzyme.
• Both describe the enzyme-substrate (ES) complex formation.

Differences between Lock and key model and induced fit model

The main differences between the lock and key model and the induced fit model are listed below.

Differences	Lock and key model	Induced fit model
Proposed	Emil Fisher	Koshland
Year	1894	1958
Definition	Perfect binding of specific substrate to a specific enzyme	Change in shape of the active site of the enzyme is induced upon binding with substrate
Shape	No shape change	Conformational changes
Enzyme	A rigid structure like a lock	Flexible structure
Active site	Complementary to substrate	Non-complementary to substrate
Substrate	Single substrate binding	Binding with variety of related substrate
Nature of binding	The substrate binds tightly to the active site	Flexible binding of substrate
Transition-state	Does not explain	Explain

Here is diagram to illustrate differences between lock and key model and induced fit model.

Lock and Key Model vs Induced Fit Model

References

• Keil, B. (2012). Specificity of proteolysis. Springer Science & Business Media.
• Vocadlo, D. J. (2012). O-GlcNAc processing enzymes: catalytic mechanisms, substrate specificity, and enzyme regulation. Current opinion in chemical biology, 16(5-6), 488-497.