There are two theories explaining the enzyme-substrate interaction. In the lock-and-key model, the active site of an enzyme is precisely shaped to hold specific substrates. In the induced-fit ...

Thus, induced fit ensures that the biological function of the enzyme, catalysis, is not enabled until after a proper substrate is bound. Figure 2: The classic enzymological view of induced fit.

An induced fit occurs where the active site of the enzyme is changed slightly to better fit the substrate after the substrate binds.