Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB)

In consultation with the IUPAC-IUBMB Joint Commission on Biochemical Nomenclature (JCBN)

Enzyme Nomenclature

Recommendations of the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology on the Nomenclature and Classification of Enzymes by the Reactions they Catalyse

World Wide Web version prepared by G.P. Moss
School of Physical and Chemical Sciences, Queen Mary University of London,
Mile End Road, London, E1 4NS, UK

To SEARCH for Information on Enzymes on the Database CLICK HERE.

This page contains general information on enzyme nomenclature. It includes links to individual documents, and the number of these will increase as more sections of the enzyme list are revised. Links to other relevant databases are provided. It also provides advice on how to suggest new enzymes for listing, or correction of existing entries. There is a list of abbreviations used in the database.

Historical Introduction

In Enzyme Nomenclature 1992 there was an historical introduction. This web version is slightly edited from that in the book.

Printed Version

Published in Enzyme Nomenclature 1992 [Academic Press, San Diego, California, ISBN 0-12-227164-5 (hardback), 0-12-227165-3 (paperback)] with Supplement 1 (1993), Supplement 2 (1994), Supplement 3 (1995), Supplement 4 (1997) and Supplement 5 (in Eur. J. Biochem. 1994, 223, 1-5; Eur. J. Biochem. 1995, 232, 1-6; Eur. J. Biochem. 1996, 237, 1-5; Eur. J. Biochem. 1997, 250; 1-6, and Eur. J. Biochem. 1999, 264, 610-650; respectively) [Copyright IUBMB].

Each enzyme has recorded at the end details of when first published in Enzyme Nomenclature or when added to the database and its subsequent history.

Web Version of Enzyme Nomenclature

The complete contents of Enzyme Nomenclature, 1992 (plus subsequent supplements and other changes) are listed below in enzyme number order giving just the recommended name. Each entry provides a link to details of that enzyme. Alternatively if looking for a specific reaction used in the classification of enzymes the broad outline defined by the first two numbers are given below. Each of these subclass entries is linked to a location where the category is subdivided to sub-subclasses. These in turn are linked to a list of recommended names for each enzyme in the sub-subclass.

List of Recommended Names for Enzymes

The common names of all listed enzymes are listed below, along with their EC numbers. Where an enzyme has been deleted or transferred to another EC number, this information is also indicated. Each list is linked to either separate entries for each entry or to files with up to 50 enzymes in each file.

Common Names for:List linked to:
EC 1.1 to EC 1.3separateup to 50
EC 1.4 to EC 1.97separateup to 50
EC 2.1 to EC 2.4.1separateup to 50
EC 2.4.2 to EC 2.9separateup to 50
EC 3.1 to EC 3.3separateup to 50
EC 3.4 to EC 3.12separateup to 50
EC 4separateup to 50
EC 5separateup to 50
EC 6separateup to 50
EC 7separateup to 50

Proposed additions and changes to this list are given separately (details below).

Glossary, Reaction pathways and Links to Other Databases

A start has been made in showing the pathways in which enzymes participate. Thus, for example, a link under EC (isopentenyl-diphosphate isomerase) leads to the pathway from mevalonate to terpenes, and links under EC (squalene monooxygenase) and EC (lanosterol synthase) lead to pathways of steroid formation. For other enzymes a glossary entry has been added which may be just a systematic name or a link to a graphic representation. The glossary from Enzyme Nomenclature, 1992 may also be consulted. This has been updated with subsequent glossary entries. Each enzyme entry has links to other databases. For recent entries these may not yet have been implemented on the other datebase. For details on the information provided click here.

Enzyme Supplement 6 to 24 (electronic only)

Six documents listing additions and corrections to previous entries were approved in 2000. These together form Supplement 6.

Five documents were approved in 2001 and form Supplement 7.

Three documents (six files) were approved in 2002 and form Supplement 8.

Three documents (five files) were approved in 2003 and form Supplement 9.

Three documents were approved in 2004 and form Supplement 10.

Six documents were approved in 2005 and form Supplement 11.

Four files were approved in 2006 and form Supplement 12.

Two files were approved in 2007 and form Supplement 13.

Eleven files were approved in 2008 and form Supplement 14.

Seven files were approved in 2009 and form Supplement 15.

Seven files were approved in 2010 and form Supplement 16.

Eight files were approved in 2011 and form Supplement 17.

Five files were approved in 2012 and form Supplement 18.

Three files were approved in 2013 and form Supplement 19.

Four files were approved in 2014 and form Supplement 20.

Three files were approved in 2015 and form Supplement 21.

Four files were approved in 2016 and form Supplement 22.

Four files were approved in 2017 and form Supplement 23.

Five files has been approved in 2018 and form Supplement 24.

Four files has been approved in 2019 and form Supplement 25.

Minor corrections or changes are listed separately.

The entries are © Copyright to the International Union of Biochemistry and Molecular Biology.

Proposed New Entries and Revised Entries

Proposals for new entries to the Enzyme List and revisions of previously published entries are available from the following file:

New Enzymes (last batch added November 2021)
Suggestions and comments should be made to Dr Andrew McDonald (Department of Biochemistry, Trinity College Dublin, Dublin 2, Ireland)

Criteria for inclusion

Before an enzyme can be included in the list direct experimental evidence is required that the proposed enzyme actually catalyses the reaction claimed. Close sequence similarity is not sufficient without evidence for the reaction catalysed, because only a small change in sequence is sufficient to change the activity or specificity of an enzyme. Furthermore, because classification is based solely on the reaction catalysed, there are cases where proteins of very different sequences catalyse the same reaction. The existence of an apparent gap in a biochemical pathway, are not, in themselves, sufficient for classification purposes.

How to suggest new entries and correct existing entries

Information about new enzymes or corrections to existing entries may be reported directly from these web pages or by using the form printed in the back of Enzyme Nomenclature. Advice is available on how to suggest new enzymes for listing, or corrections of existing entries. Comments and suggestions on enzyme classification and nomenclature also may be sent to Dr Andrew McDonald (Department of Biochemistry, Trinity College Dublin, Dublin 2, Ireland)

Rules for the Classification and Nomenclature of Enzymes

In Enzyme Nomenclature 1992 there was a section on general principles; recommended and systematic names; scheme of classification and numbering of enzymes; and rules for classification and nomenclature. This web version is slightly edited from that in the book.

Enzyme Subclasses

The links are to a list of sub-subclasses which in turn list the enzymes linked to separate files for each enzyme, or to a list as part of a file with up to 50 enzymes per file.

SubclassNameEnzyme file type
EC 1Oxidoreductases  
EC 1.1Acting on the CH-OH group of donorssub-subclassesup to 50
EC 1.2Acting on the aldehyde or oxo group of donorssub-subclassesup to 50
EC 1.3Acting on the CH-CH group of donorssub-subclassesup to 50
EC 1.4Acting on the CH-NH2 group of donorssub-subclassesup to 50
EC 1.5Acting on the CH-NH group of donorssub-subclassesup to 50
EC 1.6Acting on NADH or NADPHsub-subclassesup to 50
EC 1.7Acting on other nitrogenous compounds as donorssub-subclassesup to 50
EC 1.8Acting on a sulfur group of donorssub-subclassesup to 50
EC 1.9Acting on a heme group of donorssub-subclassesup to 50
EC 1.10Acting on diphenols and related substances as donorssub-subclassesup to 50
EC 1.11Acting on a peroxide as acceptorsub-subclassesup to 50
EC 1.12Acting on hydrogen as donorsub-subclassesup to 50
EC 1.13Acting on single donors with incorporation of molecular oxygen (oxygenases)sub-subclassesup to 50
EC 1.14Acting on paired donors, with incorporation or reduction of molecular oxygensub-subclassesup to 50
EC 1.15Acting on superoxide radicals as acceptorsub-subclassesup to 50
EC 1.16Oxidising metal ionssub-subclassesup to 50
EC 1.17Acting on CH or CH2 groupssub-subclassesup to 50
EC 1.18Acting on iron-sulfur proteins as donorssub-subclassesup to 50
EC 1.19Acting on reduced flavodoxin as donorsub-subclassesup to 50
EC 1.20Acting on phosphorus or arsenic in donorssub-subclassesup to 50
EC 1.21Acting on the reaction X-H + Y-H = X-Y sub-subclassesup to 50
EC 1.22Acting on halogen in donorssub-subclassesup to 50
EC 1.23Reducing C-O-C group as acceptorsub-subclassesup to 50
EC 1.97Other oxidoreductasessub-subclassesup to 50
EC 2Transferases  
EC 2.1Transferring one-carbon groupssub-subclassesup to 50
EC 2.2Transferring aldehyde or ketonic groupssub-subclassesup to 50
EC 2.3Acyltransferasessub-subclassesup to 50
EC 2.4Glycosyltransferasessub-subclassesup to 50
EC 2.5Transferring alkyl or aryl groups, other than methyl groupssub-subclassesup to 50
EC 2.6Transferring nitrogenous groupssub-subclassesup to 50
EC 2.7Transferring phosphorus-containing groupssub-subclassesup to 50
EC 2.8Transferring sulfur-containing groupssub-subclassesup to 50
EC 2.9Transferring selenium-containing groupssub-subclassesup to 50
EC 2.10Transferring molybdenum- or tungsten-containing groupssub-subclassesup to 50
EC 3Hydrolases  
EC 3.1Acting on ester bondssub-subclassesup to 50
EC 3.2Glycosylasessub-subclassesup to 50
EC 3.3Acting on ether bondssub-subclassesup to 50
EC 3.4Acting on peptide bonds (peptidases)sub-subclassesup to 50
EC 3.5Acting on carbon-nitrogen bonds, other than peptide bondssub-subclassesup to 50
EC 3.6Acting on acid anhydridessub-subclassesup to 50
EC 3.7Acting on carbon-carbon bondssub-subclassesup to 50
EC 3.8Acting on halide bondssub-subclassesup to 50
EC 3.9Acting on phosphorus-nitrogen bondssub-subclassesup to 50
EC 3.10Acting on sulfur-nitrogen bondssub-subclassesup to 50
EC 3.11Acting on carbon-phosphorus bondssub-subclassesup to 50
EC 3.12Acting on sulfur-sulfur bondssub-subclassesup to 50
EC 3.13Acting on carbon-sulfur bondssub-subclassesup to 50
EC 4Lyases  
EC 4.1Carbon-carbon lyasessub-subclassesup to 50
EC 4.2Carbon-oxygen lyasessub-subclassesup to 50
EC 4.3Carbon-nitrogen lyasessub-subclassesup to 50
EC 4.4Carbon-sulfur lyasessub-subclassesup to 50
EC 4.5Carbon-halide lyasessub-subclassesup to 50
EC 4.6Phosphorus-oxygen lyasessub-subclassesup to 50
EC 4.7Carbon-phosphorus lyasessub-subclassesup to 50
EC 4.99Other lyasessub-subclassesup to 50
EC 5Isomerases  
EC 5.1Racemases and epimerasessub-subclassesup to 50
EC 5.2cis-trans-Isomerasessub-subclassesup to 50
EC 5.3Intramolecular isomerasessub-subclassesup to 50
EC 5.4Intramolecular transferases (mutases)sub-subclassesup to 50
EC 5.5Intramolecular lyasessub-subclassesup to 50
EC 5.99Other isomerasessub-subclassesup to 50
EC 6Ligases  
EC 6.1Forming carbon—oxygen bondssub-subclassesup to 50
EC 6.2Forming carbon—sulfur bondssub-subclassesup to 50
EC 6.3Forming carbon—nitrogen bondssub-subclassesup to 50
EC 6.4Forming carbon—carbon bondssub-subclassesup to 50
EC 6.5Forming phosphoric ester bondssub-subclassesup to 50
EC 6.6Forming nitrogen—metal bondssub-subclassesup to 50
EC 7Translocases  
EC 7.1Catalysing the translocation of hydronssub-subclassesup to 50
EC 7.2Catalysing the translocation of inorganic cationssub-subclassesup to 50
EC 7.3Catalysing the translocation of inorganic anions and their chelatessub-subclassesup to 50
EC 7.4Catalysing the translocation of amino acids and peptidessub-subclassesup to 50
EC 7.5Catalysing the translocation of carbohydrates and their derivativessub-subclassesup to 50
EC 7.6Catalysing the translocation of other compoundssub-subclassesup to 50

Last update 19 November, 2021

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