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)

       6.3.1.1  aspartate---ammonia ligase

       6.3.1.2  glutamine synthetase

       6.3.1.4  aspartate---ammonia ligase (ADP-forming)

       6.3.1.5  NAD+ synthase

       6.3.1.6  glutamate---ethylamine ligase

       6.3.1.7  4-methyleneglutamate---ammonia ligase

       6.3.1.8  glutathionylspermidine synthase

       6.3.1.9  trypanothione synthase

       6.3.1.10  adenosylcobinamide-phosphate synthase

       6.3.1.11  glutamate---putrescine ligase

       6.3.1.12  D-aspartate ligase

       6.3.1.13  L-cysteine:1D-myo-inositol 2-amino-2-deoxy-alpha-D-glucopyranoside ligase

       6.3.1.14  diphthine---ammonia ligase

       6.3.1.15  8-demethylnovobiocic acid synthase

       6.3.1.17  beta-citrylglutamate synthase

       6.3.1.18  gamma-glutamylanilide synthase

       6.3.1.19  prokaryotic ubiquitin-like protein ligase

       6.3.1.20  lipoate---protein ligase

       6.3.1.21  phosphoribosylglycinamide formyltransferase 2

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

     6.3.3  Cyclo-ligases

     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