Summary
The specific pocket on an enzyme where the substrate binds and the reaction takes place.
In depth
The active site is a cleft lined with specific amino acids that bind the substrate through weak interactions and catalyse the reaction using catalytic residues. Only a small part of the enzyme forms the site; the rest maintains its shape.
Specificity arises from the complementary shape, charge and hydrophobicity.
Binding is by weak interactions, so the substrate leaves after the reaction when the product no longer fits. Catalytic strategies include acid-base catalysis, covalent catalysis (the serine of trypsin), metal ion catalysis and proximity and orientation effects, which increase the effective concentration of substrates.
Specificity is high: some enzymes distinguish between mirror-image molecules or between substrates differing by one methyl group. Others are broad, such as the liver cytochrome P450 enzymes which handle many drugs.
Example: in lysozyme the active site strains the sugar ring of bacterial wall polysaccharide, helping to split it and thus damaging bacteria in tears and saliva.
Frequently asked questions
What is Active Site?
The specific pocket on an enzyme where the substrate binds and the reaction takes place.
Which area of biology covers Active Site, and how advanced is it?
Active Site is one of the 51 topics in Biomolecules & Biochemistry. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Condensation and Hydrolysis, Induced Fit Model, Tertiary Structure.
Can you give an example of Active Site?
The serine protease active site uses a catalytic triad of serine, histidine and aspartate.
What should I learn before Active Site?
Work through the Beginner topics in Biomolecules & Biochemistry first, such as Water Properties, Carbon Chemistry, Carbohydrates, then return to Active Site. Intermediate topics assume the Beginner vocabulary.
What topics are related to Active Site?
The closest topics to Active Site are Condensation and Hydrolysis, Induced Fit Model, Tertiary Structure, Cofactors and Coenzymes. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Active Site?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Active Site. To practise the whole of Biomolecules & Biochemistry, use the Biomolecules & Biochemistry quiz.
How is Active Site different from Condensation and Hydrolysis?
Active Site: The specific pocket on an enzyme where the substrate binds and the reaction takes place. Condensation and Hydrolysis: Dehydration synthesis joins monomers by removing water, while hydrolysis splits polymers by adding water. Read both side by side and note what each one explains.
How should I study Active Site step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Condensation and Hydrolysis and explain the difference aloud. Finally, take the Biomolecules & Biochemistry quiz and come back to this page for any question you miss.