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

     3.5.1  In linear amides

     3.5.2  In cyclic amides

       3.5.2.1  barbiturase

       3.5.2.2  dihydropyrimidinase

       3.5.2.3  dihydroorotase

       3.5.2.4  carboxymethylhydantoinase

       3.5.2.5  allantoinase

       3.5.2.6  beta-lactamase

       3.5.2.7  imidazolonepropionase

       3.5.2.9  5-oxoprolinase (ATP-hydrolysing)

       3.5.2.10  creatininase

       3.5.2.11  L-lysine-lactamase

       3.5.2.12  6-aminohexanoate-cyclic-dimer hydrolase

       3.5.2.13  2,5-dioxopiperazine hydrolase

       3.5.2.14  N-methylhydantoinase (ATP-hydrolysing)

       3.5.2.15  cyanuric acid amidohydrolase

       3.5.2.16  maleimide hydrolase

       3.5.2.17  hydroxyisourate hydrolase

       3.5.2.18  enamidase

       3.5.2.19  streptothricin hydrolase

       3.5.2.20  isatin hydrolase

     3.5.3  In linear amidines

     3.5.4  In cyclic amidines

     3.5.5  In nitriles

     3.5.99  In other compounds

   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

   3.12  Acting on sulfur-sulfur bonds

   3.13  Acting on carbon-sulfur bonds

 4. Lyases

 5. Isomerases

 6. Ligases

 7. Translocases