Enzyme nomenclature was formalized in the 1950s.1 It is formulated by the International Union of Biochemistry (IUB) and the International Union of Pure and Applied Chemistry (IUPAC), more specifically, the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB) and the IUPAC-IUB Joint Commission on Biochemical Nomenclature.
There are around 3500 listed enzymes. Officially assigned names and numbers for enzymes are available at the Enzyme Nomenclature Database: http://www.chem.qmul.ac.uk/iubmb/enzyme/. Rules for enzyme nomenclature are available at http://www.chem.qmul.ac.uk/iubmb/enzyme/rules.html.
There are 3 types of enzyme name: recommended name (common, working, or trivial name), systematic name, and Enzyme Commission (EC) number. The recommended name is the name by which the enzyme is commonly known. The systematic name incorporates the reaction the enzyme catalyzes. The EC number is a unique identifier assigned to each enzyme.
Because systematic names can be unwieldy and recommended names are well known, recommended names are used in general medical publications. For unambiguous identification, the EC number, the systematic name, or both may be included at first mention.
The parts of the EC number are as follows:
serial number within sub-subclass
The enzyme classes are as follows:
Examples are shown below:
EC 18.104.22.168 (was EC 22.214.171.124)
acetyl-CoA:acetoacetyl-CoA C- acetyltransferase
DNA ligase (ATP)
poly(deoxyribonucleotide): poly(deoxyribonucleotide) ligase (AMP-forming)