Intermediate Topic 988 of 1102 Biochemistry, Environment & Industry

Active Site

The region of an enzyme where substrate binds and reaction occurs.

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In-depth explanation of Active Site

The active site is a cleft or pocket in an enzyme formed by a specific arrangement of amino acid residues and sometimes cofactors. It binds the substrate through a combination of hydrogen bonds, ionic attractions and hydrophobic contacts, which holds the substrate in the correct orientation. Catalysis occurs through mechanisms such as acid-base catalysis, covalent intermediates, metal ion assistance, and the strain and proximity effects that bring reactants together. Because only the residues in the active site touch the substrate, mutations there can abolish activity while leaving the rest of the protein intact. The active site is a central target of drug design, since inhibitors can occupy it and block the enzyme.

Going deeper: Active Site

Key ideas: A small cleft, often only 3 to 12 residues contributing, where substrate binds through hydrogen bonds, ionic interactions and hydrophobic contacts, and where catalytic residues (for example the serine, histidine, aspartate triad of chymotrypsin) perform chemistry. Competitive inhibitors resemble the substrate and compete for the site, raising apparent Km but not Vmax.

Common mistakes and connections: A mistake is imagining the active site as most of the enzyme; it is a tiny part, the rest provides scaffold and regulation. Noncompetitive inhibitors bind elsewhere (allosteric site) and lower Vmax. Links to drug design, transition state stabilization and specificity.

Visualization of Active Site

Reaction rate versus substrate concentration. As the active sites fill, the rate levels off toward Vmax, and Km is the concentration giving half of it. The interactive lesson shows this as a live animation or chart.

Worked example and use case

In chymotrypsin a serine, histidine and aspartate triad in the active site cleaves peptide bonds.

Frequently asked questions about Active Site

What is Active Site?

The region of an enzyme where substrate binds and reaction occurs.

Is Active Site a beginner, intermediate or advanced topic?

Active Site is a intermediate topic in Biochemistry, Environment & Industry. It builds on the vocabulary of beginner topics in this area.

What should I learn before Active Site?

Study these earlier topics in Biochemistry, Environment & Industry first: Denaturation, Essential Amino Acids, Enzymes.

What comes after Active Site?

The next topics in Biochemistry, Environment & Industry are Lock and Key vs Induced Fit and Cofactors and Coenzymes.

Can I practise Active Site with quizzes?

Yes. The interactive lesson includes a self-check question on Active Site, and the Biochemistry, Environment & Industry quiz draws on every topic in this area.

Where Active Site fits in Biochemistry, Environment & Industry

Active Site is topic 13 of 127 in Biochemistry, Environment & Industry.