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EC number



This article is about the Enzyme Commission codes. For the European Commission system for coding chemicals, see EC-No.

The 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, every EC number is associated with a recommended name for the respective 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. By contrast, UniProt identifiers uniquely specify a protein by its amino acid sequence.[1]

Contents

Format of number

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 tripeptide aminopeptidases have the code "EC 3.4.11.4", whose components indicate the following groups of enzymes:

  • EC 3 enzymes are hydrolases (enzymes that use water to break up some other molecule)
  • EC 3.4 are hydrolases that act on peptide bonds
  • EC 3.4.11 are those hydrolases that cleave off the amino-terminal amino acid from a polypeptide
  • EC 3.4.11.4 are those that cleave off the amino-terminal end from a tripeptide

Top level codes

Top-level EC numbers[2]
Group Reaction catalyzed Typical reaction Enzyme example(s) with trivial name
EC 1
Oxidoreductases 		To catalyze oxidation/reduction reactions; transfer of H and O atoms or electrons from one substance to another AH + B → A + BH (reduced)
A + O → AO (oxidized) 		Dehydrogenase, oxidase
EC 2
Transferases 		Transfer of a functional group from one substance to another. The group may be methyl-, acyl-, amino- or phosphate group AB + C → A + BC Transaminase, kinase
EC 3
Hydrolases 		Formation of two products from a substrate by hydrolysis AB + H2O → AOH + BH Lipase, amylase, peptidase
EC 4
Lyases 		Non-hydrolytic addition or removal of groups from substrates. C-C, C-N, C-O or C-S bonds may be cleaved RCOCOOH → RCOH + CO2
EC 5
Isomerases 		Intramolecule rearrangement, i.e. isomerization changes within a single molecule AB → BA Isomerase, mutase
EC 6
Ligases 		Join together two molecules by synthesis of new C-O, C-S, C-N or C-C bonds with simultaneous breakdown of ATP X + Y+ ATP → XY + ADP + Pi Synthetase

History

The enzyme nomenclature scheme was developed starting in 1955, when the International Congress of Biochemistry in Brussels 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.

References

  1. ^ ENZYME (Enzyme nomenclature database). ExPASy. Retrieved on 2006-03-14.
  2. ^ Moss, G.P.. Recommendations of the Nomenclature Committee. International Union of Biochemistry and Molecular Biology on the Nomenclature and Classification of Enzymes by the Reactions they Catalyse. Retrieved on 2006-03-14.

See also

v • d • e
Proteins: enzymes
TopicsActive site - Allosteric regulation - Binding site - Catalytically perfect enzyme - Coenzyme - Cofactor - Cooperativity - EC number
Enzyme catalysis - Enzyme inhibitor - Enzyme kinetics - Lineweaver-Burk plot - Michaelis-Menten kinetics - List of enzymes
TypesEC1 Oxidoreductases/list - EC2 Transferases/list - EC3 Hydrolases/list - EC4 Lyases/list - EC5 Isomerases/list - EC6 Ligases/list
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "EC_number". A list of authors is available in Wikipedia.
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