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

     5.3.4  Transposing S-S bonds

     5.3.99  Other intramolecular oxidoreductases

       5.3.99.2  prostaglandin-D synthase

       5.3.99.3  prostaglandin-E synthase

       5.3.99.4  prostaglandin-I synthase

       5.3.99.5  thromboxane-A synthase

       5.3.99.6  allene-oxide cyclase

       5.3.99.7  styrene-oxide isomerase

       5.3.99.8  capsanthin/capsorubin synthase

       5.3.99.9  neoxanthin synthase

       5.3.99.10  thiazole tautomerase

       5.3.99.11  2-keto-myo-inositol isomerase

       5.3.99.12  lachrymatory-factor synthase

   5.4  Intramolecular transferases

   5.5  Intramolecular lyases

   5.6  Isomerases altering macromolecular conformation

   5.99  Other isomerases

 6. Ligases

 7. Translocases