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Enzyme Classification Browser

Searches or browses for structures by Enzyme Commission (EC) Number. The Enzyme Classification Browser is a hierarchical representation of enzymes by the enzyme classification according to the nomenclature of the International Union of Biochemistry and Molecular Biology (IUBMB).

Structures of a particular enzyme can be searched in the browser tree by using a term or a partial or full EC number.

The enzyme browser permits the user to navigate through the hierarchy of enzyme classification to arrive at the subset of particular interest. The browser opens up the top level in the hierarchy. Clicking on the arrow/folder icons expands the respective nodes. Clicking on the name of the node will retrieve all PDB IDs assigned that EC number.

Note: Since the publication of the Enzyme Handbook IUBMB has obsoleted several EC entries either by deleting them completely or allocating them to (some times more than one) new EC entries. Some of these EC numbers are still referred by PDB entries, and they are labeled accordingly as "Deleted entries" or "Transferred entries".

Important: Make sure pop-ups are enabled in your browser (Click here to check).


  1. Search by a term

    Histidine kinase

    Type Histidine kinase in the text box above the tree and click the button "Find in Tree". The tree expands and nodes matching the keyword expand. To see the number of matching PDB structures mouse over an entry. To view the list of structures, click on a node.

  2. Search by EC number


    Type the partial EC number 3.2.1 in the search box and click the button "Find in Tree". The tree expands and all nodes 3.2.1. are highlighted in gray.

  3. Browse the enzyme classification tree


    Mouse over Transferases to see the number of structures with the term transferase. Expand the node 2.7: Transferring phosphorous-containing groups by clicking on the triangle. Mouse over 2.7.11: Protein-serine/threonine kinases to see the number of structures related to this node. Click on the 2.7.11: Protein-serine/threonine kinases to display the list of protein-serine/threonine kinases.