Abstract
The variety of different names that had been used for the same enzyme and the fact that some different enzymes were known by the same name necessitated the development of a rational system for their classification and nomenclature. The International Union of Biochemistry devised a system of classification that allows the unambiguous identification of enzymes in terms of the reactions they catalyse. This relies on a numerical system (the EC number) to class enzymes in groups according to the types of reaction catalysed and systematic naming that describes the chemical reaction involved. This is now in widespread use and the official list of enzymes classified can be found at ExplorEnz – The Enzyme Database ( http://www.enzyme‐database.org).