System of classification

The Enzyme Commission divided enzymes into 6 main classes, on the basis of the total reaction catalyzed. Each enzyme was assigned a code number; consisting of four elements, separated by dots. The first digit shows to which of the main classes the enzyme belongs, as follows:

First digit    Enzyme class                Type of reaction catalyzed

1                  Oxido-reductases           Oxidation/reduction reactions

2                  Transferases                 Transfer of an atom or group between two molecules.

3                  Hydrolases                     Hydrolysis reactions

4                  Lyases                          Removal of a group from substrate (not be hydrolysis)

5                 Isomerases                    Isomerization reactions

6                 Ligases                            The synthetic joining of two molecule.