EC number

Enzyme Commission number (EC number) is a numerical classification scheme for enzymes, based on the chemical reactions they catalyze. As a system of enzyme nomenclature, each EC number is associated with a recommended name for the respective enzyme.

Structure of EC Numbers

EC numbers are divided into four levels, with each level separated by a period. These levels are:

1. The first number classifies the enzyme based on its overall reaction type (e.g., oxidoreductases, transferases, hydrolases).
2. The second number specifies the subclass, indicating the substrate or the type of reaction.
3. The third number provides a further subdivision based on the donor, acceptor, or other specifics of the reaction.
4. The fourth number is the serial number of the enzyme in its subclass.

This hierarchical system allows for a detailed classification and easy retrieval of enzyme information.

Major Classes of Enzymes

There are six major classes of enzymes, each with its unique type of reaction they catalyze:

1. Oxidoreductases: Enzymes that catalyze oxidation-reduction reactions. 2. Transferases: Enzymes that transfer a functional group from one molecule to another. 3. Hydrolases: Enzymes that catalyze the hydrolysis of various bonds. 4. Lyases: Enzymes that cleave various bonds by means other than hydrolysis and oxidation. 5. Isomerases: Enzymes that catalyze the rearrangement of atoms within a molecule. 6. Ligases: Enzymes that join two molecules together with covalent bonds.

Importance of EC Numbers

EC numbers are crucial for the systematic identification, classification, and study of enzymes. They facilitate:

• The easy retrieval of enzyme-related data from databases.
• The comparison and contrast of enzyme functions across different species.
• The study of metabolic pathways and their regulation.
• The development of drugs and their targeting of specific enzymes in disease processes.

Finding EC Numbers

EC numbers can be found in several biochemical and molecular biology databases, such as the Enzyme Database (BRENDA), the ExPASy (Expert Protein Analysis System) Enzyme nomenclature database, and the KEGG (Kyoto Encyclopedia of Genes and Genomes) PATHWAY Database.

Updating and Maintenance of EC Numbers

The International Union of Biochemistry and Molecular Biology (IUBMB) is responsible for the maintenance and updating of the EC number system. New enzymes and their classifications are regularly added to the system as more is understood about enzyme functions and new enzymes are discovered.

See Also

• Protein
• Metabolism
• Bioinformatics
• Molecular biology