1. Oxidoreductases

 2. Transferases

 3. Hydrolases

 4. Lyases

 5. Isomerases

   5.1  Racemases and epimerases

   5.2  cis-trans-Isomerases

   5.3  Intramolecular oxidoreductases

   5.4  Intramolecular transferases

   5.5  Intramolecular lyases

     5.5.1  Intramolecular lyases (only sub-subclass identified to date)

       5.5.1.1  muconate cycloisomerase

       5.5.1.2  3-carboxy-cis,cis-muconate cycloisomerase

       5.5.1.3  tetrahydroxypteridine cycloisomerase

       5.5.1.4  inositol-3-phosphate synthase

       5.5.1.5  carboxy-cis,cis-muconate cyclase

       5.5.1.6  chalcone isomerase

       5.5.1.7  chloromuconate cycloisomerase

       5.5.1.8  (+)-bornyl diphosphate synthase

       5.5.1.9  cycloeucalenol cycloisomerase

       5.5.1.10  alpha-pinene-oxide decyclase

       5.5.1.11  dichloromuconate cycloisomerase

       5.5.1.12  copalyl diphosphate synthase

       5.5.1.13  ent-copalyl diphosphate synthase

       5.5.1.14  syn-copalyl-diphosphate synthase

       5.5.1.15  terpentedienyl-diphosphate synthase

       5.5.1.16  halimadienyl-diphosphate synthase

       5.5.1.17  (S)-beta-macrocarpene synthase

       5.5.1.18  lycopene epsilon-cyclase

       5.5.1.19  lycopene beta-cyclase

       5.5.1.20  prosolanapyrone-III cycloisomerase

       5.5.1.22  (-)-bornyl diphosphate synthase

       5.5.1.23  aklanonic acid methyl ester cyclase

       5.5.1.24  tocopherol cyclase

       5.5.1.25  3,6-anhydro-L-galactonate cycloisomerase

       5.5.1.26  nogalonic acid methyl ester cyclase

       5.5.1.27  D-galactarolactone cycloisomerase

       5.5.1.28  (-)-kolavenyl diphosphate synthase

       5.5.1.29  (+)-kolavenyl diphosphate synthase

       5.5.1.30  labda-7,13-dienyl diphosphate synthase

       5.5.1.31  hapalindole H synthase

       5.5.1.32  12-epi-hapalindole U synthase

       5.5.1.33  12-epi-fischerindole U synthase

       5.5.1.34  (+)-cis,trans-nepetalactol synthase

       5.5.1.35  (+)-cis,cis-nepetalactol synthase

       5.5.1.36  hapalindole U synthase

   5.6  Isomerases altering macromolecular conformation

   5.99  Other isomerases

 6. Ligases

 7. Translocases