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As a system of enzyme nomenclature, every EC number is associated with a recommended name for the respective enzyme.

Every enzyme code consists of the letters "EC" followed by four numbers separated by periods. Those numbers represent a progressively finer classification of the enzyme. For example, the enzyme tripeptide aminopeptidase has the code EC 3.4.11.4 which is constructed as follows: 3 stands for hydrolases (enzymes that use water to break up some other molecule), 3.4 for hydrolases that act on peptide bonds, 3.4.11 for those that cleave off the amino-terminal amino acid from a polypeptide, and 3.4.11.4 for those that cleave off the amino-terminal end from a tripeptide.

The toplevel classification is

• EC 1 Oxidoreductases: catalyze oxidation/reduction reactions
• EC 2 Transferases: transfer a functional group (e.g. a methyl or phosphate group)
• EC 3 Hydrolases: catalyze the hydrolysis of various bonds
• EC 4 Lyases: cleave various bonds by means other than hydrolysis and oxidation
• EC 5 IsomeraseIn biochemistry, an isomerase is an enzyme which catalyses changes within one molecule, often by re-arranging the functional groups and converting the molecule into one of its isomeric forms. They are classified as EC 5 in the EC number classification.s: catalyze isomerIn chemistry, isomers are molecules with the same chemical formula and often with the same kinds of bonds between atoms, but in which the atoms are arranged differently. Many isomers share similar if not identical properties in most chemical contexts.ization changes within a single molecule
• EC 6 LigaseIn biochemistry, a ligase is an enzyme that can catalyse the joining of two molecules ("ligation" or "glue together") by forming a new chemical bond, with concomitant hydrolysis of ATP or other similar molecules. They are classified as EC 6 in the EC numbs: join two molecules with covalent bondCovalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons, by two atoms, in order to produce a mutual attraction, which holds the resultant molecule together. Atoms tend to share electrons in such a ways

The complete nomenclature can be browsed at http://www.chem.qmul.ac.uk/iubmb/enzyme/

Strictly speaking, EC numbers do not specify enzymes, but enzyme catalyzed reactions. If different enzymes (for instance from different organisms) catalyze the same reaction, then they receive the same EC number. To uniquely specify a protein by its amino acid sequence, Swiss-ProtSwiss-Prot is a curated biological database of protein sequences created in 1986 by Amos Bairoch during his PhD and developed by the Swiss Institute of Bioinformatics and the European Bioinformatics Institute. It strives to provide a high level of annotat identifiers can be used. An EC tree that is cross-linked with the corresponding Swiss-Prot entries, as well as with other databases and a MedlineMedline is a comprehensive literature database of life sciences and biomedical information. It covers the fields of medicine, nursing, dentistry, veterinary medicine and the health care system. As perhaps a side effect of covering these fields, it also ma literature search, is available at http://www.expasy.org/enzyme/

The enzyme nomenclature scheme was developed starting in 19551955 is a common year starting on Saturday. see link for calendar) Events January events January 2 Panama president Jose Antonio Remon is assassinated. January 19 The Scrabble board game debuts. February events February 8 Nikolai Bulganin ousts Georgi Mal, when the International Congress of Biochemistry in BrusselsBrussels ( French: Bruxelles Dutch: Brussel German: Brussel is a major city in Belgium and its capital. Overview Brussels is first of all a city located in the middle of Belgium and its capital, but it sometimes also refers to the main municipality of the set up an Enzyme Commission. The first version was published in 1961. The current sixth edition, published by the International Union of Biochemistry and Molecular Biology in 1992, contains 3196 different enzymes.

See also: TC number (classification of membrane transport proteins)