Active site

This subsection of the ‘Sequence annotation (Features)’ section is used for enzymes and indicates the residues directly involved in catalysis.

Example: Q9F6D4

When the exact role of an active site residue is known, this is indicated using a semi-controlled vocabulary in the ‘Description’ field. The possible roles are:

• Charge relay system
• Electrophile
• Nucleophile
• Proton donor
• Proton acceptor

Example: Q9ZTP5

In the case of viral polyproteins or multifunctional enzymes, the name of the specific enzymatic activity involving the ‘active site’ residue is indicated in the ‘Description’ field.
Example: P12276

Nucleophiles give rise to short-lived covalent intermediates. Whenever possible, we indicate the exact chemical nature of the intermediate, using a semi-controlled vocabulary.
Example: P27796

Each ‘Active site’ subsection refers to a single amino acid. There can be one or several ‘Active site’ subsections, depending on the nature of the catalytic mechanism.

When the catalytic activity is brought about by bound metal ions or water molecules, or by direct contact between substrate and cofactor, we do not add any ‘Active site’ subsection.