Enzyme Nomenclature

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 1.3	separate	up to 50
EC 1.4 to EC 1.97	separate	up to 50
EC 2.1 to EC 2.4.1	separate	up to 50
EC 2.4.2 to EC 2.9	separate	up to 50
EC 3.1 to EC 3.3	separate	up to 50
EC 3.4 to EC 3.12	separate	up to 50
EC 4	separate	up to 50
EC 5	separate	up to 50
EC 6	separate	up to 50
EC 7	separate	up to 50

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 5.3.3.2 (isopentenyl-diphosphate isomerase) leads to the pathway from mevalonate to terpenes, and links under EC 1.14.99.7 (squalene monooxygenase) and EC 5.4.99.7 (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.

Four files has been approved in 2020 and form Supplement 26.

Three files has been approved in 2021 and form Supplement 27.

Four files has been approved in 2022 and form Supplement 28.

Two files has been approved in 2023 and form Supplement 29.

One files has been approved in 2024 and form Supplement 30.

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 March 2024)

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.

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

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