Enzyme Commission number

(Abbreviation: EC number). Systematic label which identifies an enzyme in the technical literature. Consists of four numbers separated by dots: the first classifies the enzyme into one of the six broad enzyme groups (see: enzymes ); each group is subdivided into sub-groups, each sub-group into sub-sub-groups, and the last number is specific for the enzyme, e.g. EC 3.1.21.1 is deoxyribonuclease I.