Lock and Key Model: Definition, Function, and Examples

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Lock and Key Model Definition

A paradigm for enzyme-substrate interaction suggests the enzyme and substrate have complimentary geometric forms that fit perfectly together. Enzymes have a high level of specificity. Before they may catalyse a chemical process, they must first attach to a particular substrate.

At the moment, two models are used to describe enzyme specificity:

(1) The lock and key model 

(2) The induced fit model

The enzyme-substrate interaction in the lock-and-key paradigm implies that the enzyme and the substrate have complimentary geometric forms that fit perfectly together.

Only the right size and form of the substrate (the key) would fit into the active site (the key hole) of the enzyme, similar to a key into a lock (the lock).

According to the induced fit model proposed by Daniel Koshland in 1958, the active site changes until the substrate is entirely bonded to the enzyme’s active site, at which time the final shape and charge are established.

The induced fit model, in contrast to the lock-and-key paradigm, demonstrates that enzymes are very flexible structures.

Emil Fischer proposed the lock and key model hypothesis in 1894, which demonstrates the great specificity of enzymes. It does not, however, explain the enzymes’ ability to stabilise the transition state.

Lock and Key Model Citations


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