1. Oxidoreductases

 2. Transferases

 3. Hydrolases

 4. Lyases

 5. Isomerases

 6. Ligases

   6.1  Forming carbon-oxygen bonds

   6.2  Forming carbon-sulfur bonds

   6.3  Forming carbon-nitrogen bonds

     6.3.1  Acid-D-ammonia (or amine) ligases (amide synthases)

     6.3.2  Acid-D-amino-acid ligases (peptide synthases)

     6.3.3  Cyclo-ligases

       6.3.3.1  phosphoribosylformylglycinamidine cyclo-ligase

       6.3.3.2  5-formyltetrahydrofolate cyclo-ligase

       6.3.3.3  dethiobiotin synthase

       6.3.3.4  (carboxyethyl)arginine beta-lactam-synthase

       6.3.3.5  O-ureido-D-serine cyclo-ligase

       6.3.3.6  carbapenam-3-carboxylate synthase

       6.3.3.7  Ni-sirohydrochlorin a,c-diamide reductive cyclase

     6.3.4  Other carbon-nitrogen ligases

     6.3.5  Carbon-nitrogen ligases with glutamine as amido-N-donor

   6.4  Forming carbon-carbon bonds

   6.5  Forming phosphoric-ester bonds

   6.6  Forming nitrogen-metal bonds

   6.7  Forming nitrogen-nitrogen bonds

 7. Translocases