The lock-and-key model and induced fit model of enzyme-substrate interaction.

– These are two models that attempt to describe how enzymes bind to their substrates and catalyze chemical reactions.

– The lock-and-key model was first proposed by Emil Fischer in 1894.

It suggests that the enzyme and the substrate have specific complementary shapes that fit exactly into each other, like a key into a lock. The active site of the enzyme is the part that binds to the substrate and has a fixed shape that matches only one type of substrate.

– This model explains the high specificity of enzymes, but it does not account for the stabilization of the transition state or the flexibility of the enzyme and substrate.

– The induced fit model was proposed by Daniel Koshland in 1958.

It suggests that the enzyme and the substrate undergo dynamic conformational changes when they interact, resulting in a better fit between them. The active site of the enzyme is not rigid, but rather adapts to the shape of the substrate as it binds.

– This model explains how enzymes can lower the activation energy and accelerate the reaction rate, as well as how they can bind to different substrates with similar structures.

Both models are useful for understanding enzyme-substrate interaction, but neither is completely accurate. The reality is probably somewhere between the two extremes, where some enzymes have more rigid active sites and others have more flexible ones. The degree of fit between the enzyme and the substrate may also vary depending on the type and strength of the interactions involved.