1. Oxidoreductases

 2. Transferases

 3. Hydrolases

 4. Lyases

 5. Isomerases

   5.1  Racemases and epimerases

   5.2  cis-trans-Isomerases

   5.3  Intramolecular oxidoreductases

     5.3.1  Interconverting aldoses and ketoses, and related compounds

     5.3.2  Interconverting keto- and enol-groups

     5.3.3  Transposing C=C bonds

       5.3.3.1  steroid Delta-isomerase

       5.3.3.2  isopentenyl-diphosphate Delta-isomerase

       5.3.3.3  vinylacetyl-CoA Delta-isomerase

       5.3.3.4  muconolactone Delta-isomerase

       5.3.3.5  cholestenol Delta-isomerase

       5.3.3.6  methylitaconate Delta-isomerase

       5.3.3.7  aconitate Delta-isomerase

       5.3.3.8  Delta3-Delta2-enoyl-CoA isomerase

       5.3.3.9  prostaglandin-A1 Delta-isomerase

       5.3.3.10  5-carboxymethyl-2-hydroxymuconate Delta-isomerase

       5.3.3.11  isopiperitenone Delta-isomerase

       5.3.3.12  L-dopachrome isomerase

       5.3.3.13  polyenoic fatty acid isomerase

       5.3.3.14  trans-2-decenoyl-[acyl-carrier protein] isomerase

       5.3.3.17  trans-2,3-dihydro-3-hydroxyanthranilate isomerase

       5.3.3.18  2-(1,2-epoxy-1,2-dihydrophenyl)acetyl-CoA isomerase

       5.3.3.19  3-[(4R)-4-hydroxycyclohexa-1,5-dien-1-yl]-2-oxopropanoate isomerase

       5.3.3.21  Delta3,5-Delta2,4-dienoyl-CoA isomerase

       5.3.3.22  lutein isomerase

       5.3.3.23  S-methyl-5-thioribulose 1-phosphate isomerase

       5.3.3.24  neopinone isomerase

     5.3.4  Transposing S-S bonds

     5.3.99  Other intramolecular oxidoreductases

   5.4  Intramolecular transferases

   5.5  Intramolecular lyases

   5.6  Isomerases altering macromolecular conformation

   5.99  Other isomerases

 6. Ligases

 7. Translocases