Enzymes: Classification and Nomenclature

Enzymes are biological catalysts -- substances that speed up the rate of a specific biochemical reaction without themselves being permanently altered or consumed in the process -- and, with the notable exception of a small group of catalytic RNA molecules called ribozymes, virtually every enzyme is a protein. An enzyme works by lowering the activation energy required for a reaction to proceed, allowing reactions that would otherwise occur imperceptibly slowly at body temperature to take place fast enough to sustain life.

Individual enzymes are traditionally known by a trivial or common name, very often formed by adding the suffix "-ase" to the name of the substrate on which the enzyme acts (as in amylase, which acts on starch, or protease, which acts on protein) or to the type of reaction it catalyses (as in dehydrogenase, which removes hydrogen). Because this system produced many inconsistent and overlapping names as more enzymes were discovered, the International Union of Biochemistry and Molecular Biology (IUBMB) established a systematic scheme that assigns every enzyme a unique four-part Enzyme Commission (EC) number and sorts all enzymes into six major classes according to the general type of reaction they catalyse. …