Editing Enzyme Commission number (section)

{{Short description|Chemical numbering scheme}}
{{Distinguish|European Community number}}
The '''Enzyme Commission number''' ('''EC number''') is a [[numbering scheme|numerical classification]] scheme for [[enzyme]]s, based on the [[chemical reaction]]s they [[catalysis|catalyze]].<ref name="isbn0-12-227164-5">{{cite book |last=Webb |first=E. C. |title=Enzyme nomenclature 1992: recommendations of the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology on the nomenclature and classification of enzymes |publisher=Academic Press |year=1992 |isbn=978-0-12-227164-9 |url=https://archive.org/details/enzymenomenclatu0000inte_d6c2 |url-access=registration }}</ref> As a system of '''enzyme nomenclature''', every EC number is associated with a recommended name for the corresponding enzyme-catalyzed reaction.

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.<ref name='expasy'>{{cite web|publisher=ExPASy |title=ENZYME (Enzyme nomenclature database) |url=http://www.expasy.org/enzyme/ |access-date=24 April 2019 |url-status=live |archive-url=https://web.archive.org/web/20190321195549/https://enzyme.expasy.org/ |archive-date=21 March 2019}}</ref> Furthermore, through [[convergent evolution]], completely different [[protein fold class|protein folds]] can catalyze an identical reaction (these are sometimes called [[non-homologous isofunctional enzymes]])<ref name="pmid20433725">{{cite journal|vauthors=Omelchenko MV, Galperin MY, Wolf YI, Koonin EV |title=Non-homologous isofunctional enzymes: a systematic analysis of alternative solutions in enzyme evolution |journal=Biology Direct |volume=5 |issue=1 |page=31 |year=2010 |pmid=20433725 |pmc=2876114 |doi=10.1186/1745-6150-5-31 |doi-access=free }}</ref>  and therefore would be assigned the same EC number. By contrast, [[UniProt]] identifiers uniquely specify a protein by its amino acid sequence.<ref name="pmid14681372">{{cite journal|vauthors=Apweiler R, Bairoch A, Wu CH, Barker WC, Boeckmann B, Ferro S, Gasteiger E, Huang H, Lopez R, Magrane M, Martin MJ, Natale DA, O'Donovan C, Redaschi N, Yeh LS |title=UniProt: the Universal Protein knowledgebase |journal=Nucleic Acids Research |volume=32 |issue=Database issue |pages=D115–9 |date=Jan 2004 |pmid=14681372 |pmc=308865 |doi=10.1093/nar/gkh131}}</ref>