1. Oxidoreductases

 2. Transferases

 3. Hydrolases

   3.1  Acting on ester bonds

   3.2  Glycosylases

   3.3  Acting on ether bonds

   3.4  Acting on peptide bonds (peptidases)

   3.5  Acting on carbon-nitrogen bonds, other than peptide bonds

   3.6  Acting on acid anhydrides

   3.7  Acting on carbon-carbon bonds

   3.8  Acting on halide bonds

   3.9  Acting on phosphorus-nitrogen bonds

   3.10  Acting on sulfur-nitrogen bonds

   3.11  Acting on carbon-phosphorus bonds

     3.11.1  Acting on carbon-phosphorus bonds (only sub-subclass identified to date)

       3.11.1.1  phosphonoacetaldehyde hydrolase

       3.11.1.2  phosphonoacetate hydrolase

       3.11.1.3  phosphonopyruvate hydrolase

   3.12  Acting on sulfur-sulfur bonds

   3.13  Acting on carbon-sulfur bonds

 4. Lyases

 5. Isomerases

 6. Ligases

 7. Translocases