1. Oxidoreductases

 2. Transferases

 3. Hydrolases

 4. Lyases

 5. Isomerases

   5.1  Racemases and epimerases

     5.1.1  Acting on amino acids and derivatives

     5.1.2  Acting on hydroxy acids and derivatives

       5.1.2.1  lactate racemase

       5.1.2.2  mandelate racemase

       5.1.2.3  3-hydroxybutyryl-CoA epimerase

       5.1.2.4  acetoin racemase

       5.1.2.5  tartrate epimerase

       5.1.2.6  isocitrate epimerase

       5.1.2.7  tagaturonate epimerase

     5.1.3  Acting on carbohydrates and derivatives

     5.1.99  Acting on other compounds

   5.2  cis-trans-Isomerases

   5.3  Intramolecular oxidoreductases

   5.4  Intramolecular transferases

   5.5  Intramolecular lyases

   5.6  Isomerases altering macromolecular conformation

   5.99  Other isomerases

 6. Ligases

 7. Translocases