Models of enzyme function
There are several theories suggesting how enzymes decrease the activation energy of reactions.
One popular theory is called the lock-and-key hypothesis:
- The substrate (the key) binds to the active site of the enzyme (the lock).
- This forms an enzyme-substrate complex (ES-complex).
- The ES-complex lowers the activation energy of the reaction, allowing it to occur.
- The products of the reaction do not fit the active site. They are quickly removed.
The substrate and active site have complementary shapes.
The lock-and-key hypothesis is a simple but inaccurate way of understanding enzyme function. The induced fit model is a more accurate version of the lock-and-key hypothesis.
In the induced fit model, the binding of the substrate causes the enzyme to change shape. The shape change activates the enzyme, enabling it to act as a catalyst.