Nomenclature and ENZYME Database

The widely accepted basis of all enzyme classifications are the recommendations of the Enzyme Committee (E.C.) of the International Union of Biochemistry and Molecular Biology (IUBMB)1491. Within this system, enzymatic activities are classified by a four-level hierarchy and each entry is described by a set of four numbers. The first number describes the top level and can be either 1 for oxidoreductases, 2 for transferases, 3 for hydrolases, 4 for lyases, 5 for isomerases or 6 for ligases. The meaning of the three lower hierarchy levels depends on the top level group. As an example, glycogen synthase is classified as 2.4.1.11 here, the 2 stands for transferases, the 4 for glycosyl-transferases, the 1 for hexosyl-transferases and the 11 for the particular subfamily. 

The ENZYME database1501, maintained by the Swiss Institute for Bioinformatics (SIB), provides a comprehensive list of all IUBMB classifications, together with associated information such as systematic and alternative enzyme names, cofactor requirements, and pointers to the corresponding entry in the SWISS-PROT database of protein sequences1511. In addition, there is a concise free-text description of the reaction catalyzed, together with a description of preferential substrates and products. Currently, the ENZYME database holds entries for approximately 3700 enzymes. 

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