The lock-and-key model

The lock-and-key model was one of the earliest models to describe the way substrates interact with enzymes.

The lock-and-key model proposes that an enzyme's substrate fits perfectly into the active site: the way a key fits into a lock.*

Enzymology: 3. Active Site & Regulation

key features of the enzyme active site

The active site of an enzyme is a 3-dimensional cleft in the enzyme that forms a pocket in which the substrate can bind. It's a small part of the total enzyme.
The specificity of the active site depends on the arrangement of atoms in the binding pocket.
There are two models of substrate binding in the active site:

– The lock-and-key model – The induced-fit model

Many enzymes have allosteric sites that bind effectors molecules and regulate their activity.
Enzymes can be regulated in a variety of ways.

See Enzyme Overview

See Enzyme Nomenclature

See Enzyme Kinetics and Inhibition